您应该使用 ImageView 的 onDraw() 方法，因为当视图需要在屏幕上绘制其内容时会调用该方法。
我创建了一个名为 MyImageView 的新类，它扩展了 ImageView 并覆盖了 onDraw() 方法，该方法将触发回调以让侦听器知道该视图已完成绘制
public class MyImageView extends ImageView {
private OnDrawFinishedListener mDrawFinishedListener;
public MyImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mDrawFinishedListener != null) {
mDrawFinishedListener.onOnDrawFinish();
}
}
public void setOnDrawFinishedListener(OnDrawFinishedListener listener) {
mDrawFinishedListener = listener;
}
public interface OnDrawFinishedListener {
public void onOnDrawFinish();
}
}
在 MainActivity 中，定义 3 个位图：一个对 ImageView 用于绘制的位图的引用，一个用于解码，一个对回收用于下一次解码的位图的引用。我重用了 vminorov 答案中的同步块，但在代码注释中放置了不同的地方并有解释
public class MainActivity extends Activity {
private Bitmap mDecodingBitmap;
private Bitmap mShowingBitmap;
private Bitmap mRecycledBitmap;
private final Object lock = new Object();
private volatile boolean ready = true;
ArrayList<Integer> images = new ArrayList<Integer>();
int position = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
images.add(R.drawable.black);
images.add(R.drawable.blue);
images.add(R.drawable.green);
images.add(R.drawable.grey);
images.add(R.drawable.orange);
images.add(R.drawable.pink);
images.add(R.drawable.red);
images.add(R.drawable.white);
images.add(R.drawable.yellow);
final MyImageView imageView = (MyImageView) findViewById(R.id.image);
imageView.setOnDrawFinishedListener(new OnDrawFinishedListener() {
@Override
public void onOnDrawFinish() {
/*
* The ImageView has finished its drawing, now we can recycle
* the bitmap and use the new one for the next drawing
*/
mRecycledBitmap = mShowingBitmap;
mShowingBitmap = null;
synchronized (lock) {
ready = true;
lock.notifyAll();
}
}
});
final Button goButton = (Button) findViewById(R.id.button);
goButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Runnable runnable = new Runnable() {
@Override
public void run() {
while (true) {
BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 1;
if (mDecodingBitmap != null) {
options.inBitmap = mDecodingBitmap;
}
mDecodingBitmap = BitmapFactory.decodeResource(
getResources(), images.get(position),
options);
/*
* If you want the images display in order and none
* of them is bypassed then you should stay here and
* wait until the ImageView finishes displaying the
* last bitmap, if not, remove synchronized block.
*
* It's better if we put the lock here (after the
* decoding is done) so that the image is ready to
* pass to the ImageView when this thread resume.
*/
synchronized (lock) {
while (!ready) {
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
ready = false;
}
if (mShowingBitmap == null) {
mShowingBitmap = mDecodingBitmap;
mDecodingBitmap = mRecycledBitmap;
}
runOnUiThread(new Runnable() {
@Override
public void run() {
if (mShowingBitmap != null) {
imageView
.setImageBitmap(mShowingBitmap);
/*
* At this point, nothing has been drawn
* yet, only passing the data to the
* ImageView and trigger the view to
* invalidate
*/
}
}
});
try {
Thread.sleep(5);
} catch (InterruptedException e) {
}
position++;
if (position >= images.size())
position = 0;
}
}
};
Thread t = new Thread(runnable);
t.start();
}
});
}
}