https://source.android.com/ 
/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.view;

import android.annotation.Nullable;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.SurfaceTexture;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;


A TextureView can be used to display a content stream. Such a content
stream can for instance be a video or an OpenGL scene. The content stream
can come from the application's process as well as a remote process.


TextureView can only be used in a hardware accelerated window. When
rendered in software, TextureView will draw nothing.


Unlike SurfaceView, TextureView does not create a separate window but behaves as a regular View. This key difference allows a TextureView to be moved, transformed, animated, etc. For instance, you can make a TextureView semi-translucent by calling myView.setAlpha(0.5f).


Using a TextureView is simple: all you need to do is get its SurfaceTexture. The SurfaceTexture can then be used to render content. The following example demonstrates how to render the camera preview into a TextureView:


 public class LiveCameraActivity extends Activity implements TextureView.SurfaceTextureListener {
     private Camera mCamera;
     private TextureView mTextureView;
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         mTextureView = new TextureView(this);
         mTextureView.setSurfaceTextureListener(this);
         setContentView(mTextureView);
     }
     public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
         mCamera = Camera.open();
         try {
             mCamera.setPreviewTexture(surface);
             mCamera.startPreview();
         } catch (IOException ioe) {
             // Something bad happened
         }
     }
     public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
         // Ignored, Camera does all the work for us
     }
     public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
         mCamera.stopPreview();
         mCamera.release();
         return true;
     }
     public void onSurfaceTextureUpdated(SurfaceTexture surface) {
         // Invoked every time there's a new Camera preview frame
     }
 }



A TextureView's SurfaceTexture can be obtained either by invoking getSurfaceTexture() or by using a SurfaceTextureListener. It is important to know that a SurfaceTexture is available only after the TextureView is attached to a window (and onAttachedToWindow() has been invoked.) It is therefore highly recommended you use a listener to be notified when the SurfaceTexture becomes available.


It is important to note that only one producer can use the TextureView. For instance, if you use a TextureView to display the camera preview, you cannot use lockCanvas() to draw onto the TextureView at the same time.


See Also:
/**
 * <p>A TextureView can be used to display a content stream. Such a content
 * stream can for instance be a video or an OpenGL scene. The content stream
 * can come from the application's process as well as a remote process.</p>
 *
 * <p>TextureView can only be used in a hardware accelerated window. When
 * rendered in software, TextureView will draw nothing.</p>
 *
 * <p>Unlike {@link SurfaceView}, TextureView does not create a separate
 * window but behaves as a regular View. This key difference allows a
 * TextureView to be moved, transformed, animated, etc. For instance, you
 * can make a TextureView semi-translucent by calling
 * <code>myView.setAlpha(0.5f)</code>.</p>
 *
 * <p>Using a TextureView is simple: all you need to do is get its
 * {@link SurfaceTexture}. The {@link SurfaceTexture} can then be used to
 * render content. The following example demonstrates how to render the
 * camera preview into a TextureView:</p>
 *
 * <pre>
 *  public class LiveCameraActivity extends Activity implements TextureView.SurfaceTextureListener {
 *      private Camera mCamera;
 *      private TextureView mTextureView;
 *
 *      protected void onCreate(Bundle savedInstanceState) {
 *          super.onCreate(savedInstanceState);
 *
 *          mTextureView = new TextureView(this);
 *          mTextureView.setSurfaceTextureListener(this);
 *
 *          setContentView(mTextureView);
 *      }
 *
 *      public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
 *          mCamera = Camera.open();
 *
 *          try {
 *              mCamera.setPreviewTexture(surface);
 *              mCamera.startPreview();
 *          } catch (IOException ioe) {
 *              // Something bad happened
 *          }
 *      }
 *
 *      public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
 *          // Ignored, Camera does all the work for us
 *      }
 *
 *      public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
 *          mCamera.stopPreview();
 *          mCamera.release();
 *          return true;
 *      }
 *
 *      public void onSurfaceTextureUpdated(SurfaceTexture surface) {
 *          // Invoked every time there's a new Camera preview frame
 *      }
 *  }
 * </pre>
 *
 * <p>A TextureView's SurfaceTexture can be obtained either by invoking
 * {@link #getSurfaceTexture()} or by using a {@link SurfaceTextureListener}.
 * It is important to know that a SurfaceTexture is available only after the
 * TextureView is attached to a window (and {@link #onAttachedToWindow()} has
 * been invoked.) It is therefore highly recommended you use a listener to
 * be notified when the SurfaceTexture becomes available.</p>
 *
 * <p>It is important to note that only one producer can use the TextureView.
 * For instance, if you use a TextureView to display the camera preview, you
 * cannot use {@link #lockCanvas()} to draw onto the TextureView at the same
 * time.</p>
 *
 * @see SurfaceView
 * @see SurfaceTexture
 */
public class TextureView extends View {
    private static final String LOG_TAG = "TextureView";

    private TextureLayer mLayer;
    private SurfaceTexture mSurface;
    private SurfaceTextureListener mListener;
    private boolean mHadSurface;

    private boolean mOpaque = true;

    private final Matrix mMatrix = new Matrix();
    private boolean mMatrixChanged;

    private final Object[] mLock = new Object[0];
    private boolean mUpdateLayer;
    private boolean mUpdateSurface;

    private Canvas mCanvas;
    private int mSaveCount;

    private final Object[] mNativeWindowLock = new Object[0];
    // Set by native code, do not write!
    private long mNativeWindow;

    
Creates a new TextureView.

Params:
  • context – The context to associate this view with.
/**
     * Creates a new TextureView.
     *
     * @param context The context to associate this view with.
     */
    public TextureView(Context context) {
        super(context);
    }

    
Creates a new TextureView.

Params:
  • context – The context to associate this view with.
  • attrs – The attributes of the XML tag that is inflating the view.
/**
     * Creates a new TextureView.
     *
     * @param context The context to associate this view with.
     * @param attrs The attributes of the XML tag that is inflating the view.
     */
    public TextureView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    
Creates a new TextureView.

Params:
  • context – The context to associate this view with.
  • attrs – The attributes of the XML tag that is inflating the view.
  • defStyleAttr – An attribute in the current theme that contains a
       reference to a style resource that supplies default values for
       the view. Can be 0 to not look for defaults.
/**
     * Creates a new TextureView.
     *
     * @param context The context to associate this view with.
     * @param attrs The attributes of the XML tag that is inflating the view.
     * @param defStyleAttr An attribute in the current theme that contains a
     *        reference to a style resource that supplies default values for
     *        the view. Can be 0 to not look for defaults.
     */
    public TextureView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    
Creates a new TextureView.

Params:
  • context – The context to associate this view with.
  • attrs – The attributes of the XML tag that is inflating the view.
  • defStyleAttr – An attribute in the current theme that contains a
       reference to a style resource that supplies default values for
       the view. Can be 0 to not look for defaults.
  • defStyleRes – A resource identifier of a style resource that
       supplies default values for the view, used only if
       defStyleAttr is 0 or can not be found in the theme. Can be 0
       to not look for defaults.
/**
     * Creates a new TextureView.
     *
     * @param context The context to associate this view with.
     * @param attrs The attributes of the XML tag that is inflating the view.
     * @param defStyleAttr An attribute in the current theme that contains a
     *        reference to a style resource that supplies default values for
     *        the view. Can be 0 to not look for defaults.
     * @param defStyleRes A resource identifier of a style resource that
     *        supplies default values for the view, used only if
     *        defStyleAttr is 0 or can not be found in the theme. Can be 0
     *        to not look for defaults.
     */
    public TextureView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    
{@inheritDoc}

/**
     * {@inheritDoc}
     */
    @Override
    public boolean isOpaque() {
        return mOpaque;
    }

    
Indicates whether the content of this TextureView is opaque. The
content is assumed to be opaque by default.

Params:
  • opaque – True if the content of this TextureView is opaque,
              false otherwise
/**
     * Indicates whether the content of this TextureView is opaque. The
     * content is assumed to be opaque by default.
     *
     * @param opaque True if the content of this TextureView is opaque,
     *               false otherwise
     */
    public void setOpaque(boolean opaque) {
        if (opaque != mOpaque) {
            mOpaque = opaque;
            if (mLayer != null) {
                updateLayerAndInvalidate();
            }
        }
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();

        if (!isHardwareAccelerated()) {
            Log.w(LOG_TAG, "A TextureView or a subclass can only be "
                    + "used with hardware acceleration enabled.");
        }

        if (mHadSurface) {
            invalidate(true);
            mHadSurface = false;
        }
    }

    
@hide
/** @hide */
    @Override
    protected void onDetachedFromWindowInternal() {
        destroyHardwareLayer();
        releaseSurfaceTexture();
        super.onDetachedFromWindowInternal();
    }

    
@hide
/**
     * @hide
     */
    @Override
    protected void destroyHardwareResources() {
        super.destroyHardwareResources();
        destroyHardwareLayer();
    }

    private void destroyHardwareLayer() {
        if (mLayer != null) {
            mLayer.detachSurfaceTexture();
            mLayer.destroy();
            mLayer = null;
            mMatrixChanged = true;
        }
    }

    private void releaseSurfaceTexture() {
        if (mSurface != null) {
            boolean shouldRelease = true;

            if (mListener != null) {
                shouldRelease = mListener.onSurfaceTextureDestroyed(mSurface);
            }

            synchronized (mNativeWindowLock) {
                nDestroyNativeWindow();
            }

            if (shouldRelease) {
                mSurface.release();
            }
            mSurface = null;
            mHadSurface = true;
        }
    }

    
The layer type of a TextureView is ignored since a TextureView is always
considered to act as a hardware layer. The optional paint supplied to this
method will however be taken into account when rendering the content of
this TextureView.

Params:
/**
     * The layer type of a TextureView is ignored since a TextureView is always
     * considered to act as a hardware layer. The optional paint supplied to this
     * method will however be taken into account when rendering the content of
     * this TextureView.
     *
     * @param layerType The type of layer to use with this view, must be one of
     *        {@link #LAYER_TYPE_NONE}, {@link #LAYER_TYPE_SOFTWARE} or
     *        {@link #LAYER_TYPE_HARDWARE}
     * @param paint The paint used to compose the layer. This argument is optional
     *        and can be null. It is ignored when the layer type is
     *        {@link #LAYER_TYPE_NONE}
     */
    @Override
    public void setLayerType(int layerType, @Nullable Paint paint) {
        setLayerPaint(paint);
    }

    @Override
    public void setLayerPaint(@Nullable Paint paint) {
        if (paint != mLayerPaint) {
            mLayerPaint = paint;
            invalidate();
        }
    }

    
Always returns View.LAYER_TYPE_HARDWARE. 
/**
     * Always returns {@link #LAYER_TYPE_HARDWARE}.
     */
    @Override
    public int getLayerType() {
        return LAYER_TYPE_HARDWARE;
    }

    
Calling this method has no effect.

/**
     * Calling this method has no effect.
     */
    @Override
    public void buildLayer() {
    }

    @Override
    public void setForeground(Drawable foreground) {
        if (foreground != null && !sTextureViewIgnoresDrawableSetters) {
            throw new UnsupportedOperationException(
                    "TextureView doesn't support displaying a foreground drawable");
        }
    }

    @Override
    public void setBackgroundDrawable(Drawable background) {
        if (background != null && !sTextureViewIgnoresDrawableSetters) {
            throw new UnsupportedOperationException(
                    "TextureView doesn't support displaying a background drawable");
        }
    }

    
Subclasses of TextureView cannot do their own rendering with the Canvas object. 
Params:
  • canvas – The Canvas to which the View is rendered.
/**
     * Subclasses of TextureView cannot do their own rendering
     * with the {@link Canvas} object.
     *
     * @param canvas The Canvas to which the View is rendered.
     */
    @Override
    public final void draw(Canvas canvas) {
        // NOTE: Maintain this carefully (see View#draw)
        mPrivateFlags = (mPrivateFlags & ~PFLAG_DIRTY_MASK) | PFLAG_DRAWN;

        /* Simplify drawing to guarantee the layer is the only thing drawn - so e.g. no background,
        scrolling, or fading edges. This guarantees all drawing is in the layer, so drawing
        properties (alpha, layer paint) affect all of the content of a TextureView. */

        if (canvas.isHardwareAccelerated()) {
            DisplayListCanvas displayListCanvas = (DisplayListCanvas) canvas;

            TextureLayer layer = getTextureLayer();
            if (layer != null) {
                applyUpdate();
                applyTransformMatrix();

                mLayer.setLayerPaint(mLayerPaint); // ensure layer paint is up to date
                displayListCanvas.drawTextureLayer(layer);
            }
        }
    }

    
Subclasses of TextureView cannot do their own rendering with the Canvas object. 
Params:
  • canvas – The Canvas to which the View is rendered.
/**
     * Subclasses of TextureView cannot do their own rendering
     * with the {@link Canvas} object.
     *
     * @param canvas The Canvas to which the View is rendered.
     */
    @Override
    protected final void onDraw(Canvas canvas) {
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        if (mSurface != null) {
            mSurface.setDefaultBufferSize(getWidth(), getHeight());
            updateLayer();
            if (mListener != null) {
                mListener.onSurfaceTextureSizeChanged(mSurface, getWidth(), getHeight());
            }
        }
    }

    TextureLayer getTextureLayer() {
        if (mLayer == null) {
            if (mAttachInfo == null || mAttachInfo.mThreadedRenderer == null) {
                return null;
            }

            mLayer = mAttachInfo.mThreadedRenderer.createTextureLayer();
            boolean createNewSurface = (mSurface == null);
            if (createNewSurface) {
                // Create a new SurfaceTexture for the layer.
                mSurface = new SurfaceTexture(false);
                nCreateNativeWindow(mSurface);
            }
            mLayer.setSurfaceTexture(mSurface);
            mSurface.setDefaultBufferSize(getWidth(), getHeight());
            mSurface.setOnFrameAvailableListener(mUpdateListener, mAttachInfo.mHandler);

            if (mListener != null && createNewSurface) {
                mListener.onSurfaceTextureAvailable(mSurface, getWidth(), getHeight());
            }
            mLayer.setLayerPaint(mLayerPaint);
        }

        if (mUpdateSurface) {
            // Someone has requested that we use a specific SurfaceTexture, so
            // tell mLayer about it and set the SurfaceTexture to use the
            // current view size.
            mUpdateSurface = false;

            // Since we are updating the layer, force an update to ensure its
            // parameters are correct (width, height, transform, etc.)
            updateLayer();
            mMatrixChanged = true;

            mLayer.setSurfaceTexture(mSurface);
            mSurface.setDefaultBufferSize(getWidth(), getHeight());
        }

        return mLayer;
    }

    @Override
    protected void onVisibilityChanged(View changedView, int visibility) {
        super.onVisibilityChanged(changedView, visibility);

        if (mSurface != null) {
            // When the view becomes invisible, stop updating it, it's a waste of CPU
            // To cancel updates, the easiest thing to do is simply to remove the
            // updates listener
            if (visibility == VISIBLE) {
                if (mLayer != null) {
                    mSurface.setOnFrameAvailableListener(mUpdateListener, mAttachInfo.mHandler);
                }
                updateLayerAndInvalidate();
            } else {
                mSurface.setOnFrameAvailableListener(null);
            }
        }
    }

    private void updateLayer() {
        synchronized (mLock) {
            mUpdateLayer = true;
        }
    }

    private void updateLayerAndInvalidate() {
        synchronized (mLock) {
            mUpdateLayer = true;
        }
        invalidate();
    }

    private void applyUpdate() {
        if (mLayer == null) {
            return;
        }

        synchronized (mLock) {
            if (mUpdateLayer) {
                mUpdateLayer = false;
            } else {
                return;
            }
        }

        mLayer.prepare(getWidth(), getHeight(), mOpaque);
        mLayer.updateSurfaceTexture();

        if (mListener != null) {
            mListener.onSurfaceTextureUpdated(mSurface);
        }
    }

    
Sets the transform to associate with this texture view.
The specified transform applies to the underlying surface
texture and does not affect the size or position of the view
itself, only of its content.


Some transforms might prevent the content from drawing
all the pixels contained within this view's bounds. In such
situations, make sure this texture view is not marked opaque.


Params:
  • transform – The transform to apply to the content of
       this view.
See Also:
/**
     * <p>Sets the transform to associate with this texture view.
     * The specified transform applies to the underlying surface
     * texture and does not affect the size or position of the view
     * itself, only of its content.</p>
     *
     * <p>Some transforms might prevent the content from drawing
     * all the pixels contained within this view's bounds. In such
     * situations, make sure this texture view is not marked opaque.</p>
     *
     * @param transform The transform to apply to the content of
     *        this view.
     *
     * @see #getTransform(android.graphics.Matrix)
     * @see #isOpaque()
     * @see #setOpaque(boolean)
     */
    public void setTransform(Matrix transform) {
        mMatrix.set(transform);
        mMatrixChanged = true;
        invalidateParentIfNeeded();
    }

    
Returns the transform associated with this texture view.

Params:
  • transform – The Matrix in which to copy the current transform. Can be null.
See Also:
Returns:The specified matrix if not null or a new Matrix instance otherwise.
/**
     * Returns the transform associated with this texture view.
     *
     * @param transform The {@link Matrix} in which to copy the current
     *        transform. Can be null.
     *
     * @return The specified matrix if not null or a new {@link Matrix}
     *         instance otherwise.
     *
     * @see #setTransform(android.graphics.Matrix)
     */
    public Matrix getTransform(Matrix transform) {
        if (transform == null) {
            transform = new Matrix();
        }

        transform.set(mMatrix);

        return transform;
    }

    private void applyTransformMatrix() {
        if (mMatrixChanged && mLayer != null) {
            mLayer.setTransform(mMatrix);
            mMatrixChanged = false;
        }
    }

    
Returns a Bitmap representation of the content of the associated surface texture. If the surface texture is not available, this method returns null.


The bitmap returned by this method uses the Config.ARGB_8888 pixel format and its dimensions are the same as this view's.


Do not invoke this method from a drawing method (onDraw(Canvas) for instance).


If an error occurs during the copy, an empty bitmap will be returned.


See Also:
Returns:A valid Config.ARGB_8888 bitmap, or null if the surface texture is not available or the width <= 0 or the height <= 0
/**
     * <p>Returns a {@link android.graphics.Bitmap} representation of the content
     * of the associated surface texture. If the surface texture is not available,
     * this method returns null.</p>
     *
     * <p>The bitmap returned by this method uses the {@link Bitmap.Config#ARGB_8888}
     * pixel format and its dimensions are the same as this view's.</p>
     *
     * <p><strong>Do not</strong> invoke this method from a drawing method
     * ({@link #onDraw(android.graphics.Canvas)} for instance).</p>
     *
     * <p>If an error occurs during the copy, an empty bitmap will be returned.</p>
     *
     * @return A valid {@link Bitmap.Config#ARGB_8888} bitmap, or null if the surface
     *         texture is not available or the width &lt;= 0 or the height &lt;= 0
     *
     * @see #isAvailable()
     * @see #getBitmap(android.graphics.Bitmap)
     * @see #getBitmap(int, int)
     */
    public Bitmap getBitmap() {
        return getBitmap(getWidth(), getHeight());
    }

    
Returns a Bitmap representation of the content of the associated surface texture. If the surface texture is not available, this method returns null.


The bitmap returned by this method uses the Config.ARGB_8888 pixel format.


Do not invoke this method from a drawing method (onDraw(Canvas) for instance).


If an error occurs during the copy, an empty bitmap will be returned.


Params:
  • width – The width of the bitmap to create
  • height – The height of the bitmap to create
See Also:
Returns:A valid Config.ARGB_8888 bitmap, or null if the surface texture is not available or width is <= 0 or height is <= 0
/**
     * <p>Returns a {@link android.graphics.Bitmap} representation of the content
     * of the associated surface texture. If the surface texture is not available,
     * this method returns null.</p>
     *
     * <p>The bitmap returned by this method uses the {@link Bitmap.Config#ARGB_8888}
     * pixel format.</p>
     *
     * <p><strong>Do not</strong> invoke this method from a drawing method
     * ({@link #onDraw(android.graphics.Canvas)} for instance).</p>
     *
     * <p>If an error occurs during the copy, an empty bitmap will be returned.</p>
     *
     * @param width The width of the bitmap to create
     * @param height The height of the bitmap to create
     *
     * @return A valid {@link Bitmap.Config#ARGB_8888} bitmap, or null if the surface
     *         texture is not available or width is &lt;= 0 or height is &lt;= 0
     *
     * @see #isAvailable()
     * @see #getBitmap(android.graphics.Bitmap)
     * @see #getBitmap()
     */
    public Bitmap getBitmap(int width, int height) {
        if (isAvailable() && width > 0 && height > 0) {
            return getBitmap(Bitmap.createBitmap(getResources().getDisplayMetrics(),
                    width, height, Bitmap.Config.ARGB_8888));
        }
        return null;
    }

    
Copies the content of this view's surface texture into the specified
bitmap. If the surface texture is not available, the copy is not executed.
The content of the surface texture will be scaled to fit exactly inside
the specified bitmap.


Do not invoke this method from a drawing method (onDraw(Canvas) for instance).


If an error occurs, the bitmap is left unchanged.


Params:
  • bitmap – The bitmap to copy the content of the surface texture into,
              cannot be null, all configurations are supported
Throws:
See Also:
Returns:The bitmap specified as a parameter
/**
     * <p>Copies the content of this view's surface texture into the specified
     * bitmap. If the surface texture is not available, the copy is not executed.
     * The content of the surface texture will be scaled to fit exactly inside
     * the specified bitmap.</p>
     *
     * <p><strong>Do not</strong> invoke this method from a drawing method
     * ({@link #onDraw(android.graphics.Canvas)} for instance).</p>
     *
     * <p>If an error occurs, the bitmap is left unchanged.</p>
     *
     * @param bitmap The bitmap to copy the content of the surface texture into,
     *               cannot be null, all configurations are supported
     *
     * @return The bitmap specified as a parameter
     *
     * @see #isAvailable()
     * @see #getBitmap(int, int)
     * @see #getBitmap()
     *
     * @throws IllegalStateException if the hardware rendering context cannot be
     *         acquired to capture the bitmap
     */
    public Bitmap getBitmap(Bitmap bitmap) {
        if (bitmap != null && isAvailable()) {
            applyUpdate();
            applyTransformMatrix();

            // This case can happen if the app invokes setSurfaceTexture() before
            // we are able to create the hardware layer. We can safely initialize
            // the layer here thanks to the validate() call at the beginning of
            // this method
            if (mLayer == null && mUpdateSurface) {
                getTextureLayer();
            }

            if (mLayer != null) {
                mLayer.copyInto(bitmap);
            }
        }
        return bitmap;
    }

    
Returns true if the SurfaceTexture associated with this TextureView is available for rendering. When this method returns true, getSurfaceTexture() returns a valid surface texture. 
/**
     * Returns true if the {@link SurfaceTexture} associated with this
     * TextureView is available for rendering. When this method returns
     * true, {@link #getSurfaceTexture()} returns a valid surface texture.
     */
    public boolean isAvailable() {
        return mSurface != null;
    }

    
Start editing the pixels in the surface. The returned Canvas can be used to draw into the surface's bitmap. A null is returned if the surface has not been created or otherwise cannot be edited. You will usually need to implement SurfaceTextureListener.onSurfaceTextureAvailable(SurfaceTexture, int, int) to find out when the Surface is available for use.


The content of the Surface is never preserved between unlockCanvas()
and lockCanvas(), for this reason, every pixel within the Surface area
must be written. The only exception to this rule is when a dirty
rectangle is specified, in which case, non-dirty pixels will be
preserved.


This method can only be used if the underlying surface is not already
owned by another producer. For instance, if the TextureView is being used
to render the camera's preview you cannot invoke this method.


See Also:
Returns:A Canvas used to draw into the surface.
/**
     * <p>Start editing the pixels in the surface.  The returned Canvas can be used
     * to draw into the surface's bitmap.  A null is returned if the surface has
     * not been created or otherwise cannot be edited. You will usually need
     * to implement
     * {@link SurfaceTextureListener#onSurfaceTextureAvailable(android.graphics.SurfaceTexture, int, int)}
     * to find out when the Surface is available for use.</p>
     *
     * <p>The content of the Surface is never preserved between unlockCanvas()
     * and lockCanvas(), for this reason, every pixel within the Surface area
     * must be written. The only exception to this rule is when a dirty
     * rectangle is specified, in which case, non-dirty pixels will be
     * preserved.</p>
     *
     * <p>This method can only be used if the underlying surface is not already
     * owned by another producer. For instance, if the TextureView is being used
     * to render the camera's preview you cannot invoke this method.</p>
     *
     * @return A Canvas used to draw into the surface.
     *
     * @see #lockCanvas(android.graphics.Rect)
     * @see #unlockCanvasAndPost(android.graphics.Canvas)
     */
    public Canvas lockCanvas() {
        return lockCanvas(null);
    }

    
Just like lockCanvas() but allows specification of a dirty rectangle. Every pixel within that rectangle must be written; however pixels outside the dirty rectangle will be preserved by the next call to lockCanvas(). This method can return null if the underlying surface texture is not available (see isAvailable() or if the surface texture is already connected to an image producer (for instance: the camera, OpenGL, a media player, etc.) 
Params:
  • dirty – Area of the surface that will be modified.
See Also:
Returns:A Canvas used to draw into the surface.
/**
     * Just like {@link #lockCanvas()} but allows specification of a dirty
     * rectangle. Every pixel within that rectangle must be written; however
     * pixels outside the dirty rectangle will be preserved by the next call
     * to lockCanvas().
     *
     * This method can return null if the underlying surface texture is not
     * available (see {@link #isAvailable()} or if the surface texture is
     * already connected to an image producer (for instance: the camera,
     * OpenGL, a media player, etc.)
     *
     * @param dirty Area of the surface that will be modified.

     * @return A Canvas used to draw into the surface.
     *
     * @see #lockCanvas()
     * @see #unlockCanvasAndPost(android.graphics.Canvas)
     * @see #isAvailable()
     */
    public Canvas lockCanvas(Rect dirty) {
        if (!isAvailable()) return null;

        if (mCanvas == null) {
            mCanvas = new Canvas();
        }

        synchronized (mNativeWindowLock) {
            if (!nLockCanvas(mNativeWindow, mCanvas, dirty)) {
                return null;
            }
        }
        mSaveCount = mCanvas.save();

        return mCanvas;
    }

    
Finish editing pixels in the surface. After this call, the surface's
current pixels will be shown on the screen, but its content is lost,
in particular there is no guarantee that the content of the Surface
will remain unchanged when lockCanvas() is called again.

Params:
  • canvas – The Canvas previously returned by lockCanvas()
See Also:
/**
     * Finish editing pixels in the surface. After this call, the surface's
     * current pixels will be shown on the screen, but its content is lost,
     * in particular there is no guarantee that the content of the Surface
     * will remain unchanged when lockCanvas() is called again.
     *
     * @param canvas The Canvas previously returned by lockCanvas()
     *
     * @see #lockCanvas()
     * @see #lockCanvas(android.graphics.Rect)
     */
    public void unlockCanvasAndPost(Canvas canvas) {
        if (mCanvas != null && canvas == mCanvas) {
            canvas.restoreToCount(mSaveCount);
            mSaveCount = 0;

            synchronized (mNativeWindowLock) {
                nUnlockCanvasAndPost(mNativeWindow, mCanvas);
            }
        }
    }

    
Returns the SurfaceTexture used by this view. This method may return null if the view is not attached to a window or if the surface texture has not been initialized yet. 
See Also:
/**
     * Returns the {@link SurfaceTexture} used by this view. This method
     * may return null if the view is not attached to a window or if the surface
     * texture has not been initialized yet.
     *
     * @see #isAvailable()
     */
    public SurfaceTexture getSurfaceTexture() {
        return mSurface;
    }

    
Set the SurfaceTexture for this view to use. If a SurfaceTexture is already being used by this view, it is immediately released and not usable any more. The SurfaceTextureListener.onSurfaceTextureDestroyed callback is not called for the previous SurfaceTexture. Similarly, the SurfaceTextureListener.onSurfaceTextureAvailable callback is not called for the SurfaceTexture passed to setSurfaceTexture. The SurfaceTexture object must be detached from all OpenGL ES contexts prior to calling this method. 
Params:
See Also:
/**
     * Set the {@link SurfaceTexture} for this view to use. If a {@link
     * SurfaceTexture} is already being used by this view, it is immediately
     * released and not usable any more.  The {@link
     * SurfaceTextureListener#onSurfaceTextureDestroyed} callback is <b>not</b>
     * called for the previous {@link SurfaceTexture}.  Similarly, the {@link
     * SurfaceTextureListener#onSurfaceTextureAvailable} callback is <b>not</b>
     * called for the {@link SurfaceTexture} passed to setSurfaceTexture.
     *
     * The {@link SurfaceTexture} object must be detached from all OpenGL ES
     * contexts prior to calling this method.
     *
     * @param surfaceTexture The {@link SurfaceTexture} that the view should use.
     * @see SurfaceTexture#detachFromGLContext()
     */
    public void setSurfaceTexture(SurfaceTexture surfaceTexture) {
        if (surfaceTexture == null) {
            throw new NullPointerException("surfaceTexture must not be null");
        }
        if (surfaceTexture == mSurface) {
            throw new IllegalArgumentException("Trying to setSurfaceTexture to " +
                    "the same SurfaceTexture that's already set.");
        }
        if (surfaceTexture.isReleased()) {
            throw new IllegalArgumentException("Cannot setSurfaceTexture to a " +
                    "released SurfaceTexture");
        }
        if (mSurface != null) {
            nDestroyNativeWindow();
            mSurface.release();
        }
        mSurface = surfaceTexture;
        nCreateNativeWindow(mSurface);

        /*
         * If the view is visible and we already made a layer, update the
         * listener in the new surface to use the existing listener in the view.
         * Otherwise this will be called when the view becomes visible or the
         * layer is created
         */
        if (((mViewFlags & VISIBILITY_MASK) == VISIBLE) && mLayer != null) {
            mSurface.setOnFrameAvailableListener(mUpdateListener, mAttachInfo.mHandler);
        }
        mUpdateSurface = true;
        invalidateParentIfNeeded();
    }

    
Returns the SurfaceTextureListener currently associated with this texture view. 
See Also:
/**
     * Returns the {@link SurfaceTextureListener} currently associated with this
     * texture view.
     *
     * @see #setSurfaceTextureListener(android.view.TextureView.SurfaceTextureListener)
     * @see SurfaceTextureListener
     */
    public SurfaceTextureListener getSurfaceTextureListener() {
        return mListener;
    }

    
Sets the SurfaceTextureListener used to listen to surface texture events. 
See Also:
/**
     * Sets the {@link SurfaceTextureListener} used to listen to surface
     * texture events.
     *
     * @see #getSurfaceTextureListener()
     * @see SurfaceTextureListener
     */
    public void setSurfaceTextureListener(SurfaceTextureListener listener) {
        mListener = listener;
    }

    private final SurfaceTexture.OnFrameAvailableListener mUpdateListener =
            new SurfaceTexture.OnFrameAvailableListener() {
        @Override
        public void onFrameAvailable(SurfaceTexture surfaceTexture) {
            updateLayer();
            invalidate();
        }
    };

    
This listener can be used to be notified when the surface texture
associated with this texture view is available.

/**
     * This listener can be used to be notified when the surface texture
     * associated with this texture view is available.
     */
    public static interface SurfaceTextureListener {
        
Invoked when a TextureView's SurfaceTexture is ready for use. 
Params:
/**
         * Invoked when a {@link TextureView}'s SurfaceTexture is ready for use.
         *
         * @param surface The surface returned by
         *                {@link android.view.TextureView#getSurfaceTexture()}
         * @param width The width of the surface
         * @param height The height of the surface
         */
        public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height);

        
Invoked when the SurfaceTexture's buffers size changed. 
Params:
/**
         * Invoked when the {@link SurfaceTexture}'s buffers size changed.
         *
         * @param surface The surface returned by
         *                {@link android.view.TextureView#getSurfaceTexture()}
         * @param width The new width of the surface
         * @param height The new height of the surface
         */
        public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height);

        
Invoked when the specified SurfaceTexture is about to be destroyed. If returns true, no rendering should happen inside the surface texture after this method is invoked. If returns false, the client needs to call SurfaceTexture.release(). Most applications should return true. 
Params:
  • surface – The surface about to be destroyed
/**
         * Invoked when the specified {@link SurfaceTexture} is about to be destroyed.
         * If returns true, no rendering should happen inside the surface texture after this method
         * is invoked. If returns false, the client needs to call {@link SurfaceTexture#release()}.
         * Most applications should return true.
         *
         * @param surface The surface about to be destroyed
         */
        public boolean onSurfaceTextureDestroyed(SurfaceTexture surface);

        
Invoked when the specified SurfaceTexture is updated through SurfaceTexture.updateTexImage(). 
Params:
  • surface – The surface just updated
/**
         * Invoked when the specified {@link SurfaceTexture} is updated through
         * {@link SurfaceTexture#updateTexImage()}.
         *
         * @param surface The surface just updated
         */
        public void onSurfaceTextureUpdated(SurfaceTexture surface);
    }

    private native void nCreateNativeWindow(SurfaceTexture surface);
    private native void nDestroyNativeWindow();

    private static native boolean nLockCanvas(long nativeWindow, Canvas canvas, Rect dirty);
    private static native void nUnlockCanvasAndPost(long nativeWindow, Canvas canvas);
}