android - View.invalidate() 非常慢。备择方案？

Question

我正在用 native 代码做一些位图动画，所以我需要每帧重绘 ImageView:

class MyImageView extends ImageView
{
    ...

    protected void onDraw( Canvas canvas )
    {
        native_drawStuff( handle, canvas );
        invalidate();
    }
}

看起来一切都很好，除了 Traceview 显示:

我不了解你，但这似乎有点荒谬。 native_drawStuff() 正在设置位图的每个像素，然后将位图绘制到 Canvas 上，而一个简单的 invalidate() 调用花费的时间几乎是 4 倍？位图也不小(RGBA_8888 和从 50k 到 300k 像素的任何地方)。

鉴于我需要在每一帧重绘整个 ImageView，是否有更好的方法来做到这一点？我看到的关于此的唯一建议是只使 View 中需要重绘的部分无效，但在我的情况下，这就是全部。

Answer 1

API 14 为此引入了完美的类:TextureView

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.

Romain Guy 在此处发布了一个如何将内容从另一个线程流式传输到 TextureView 的示例:https://groups.google.com/forum/#!topic/android-developers/_Ogjc8sozpA .我在这里复制它以供后代使用:

import android.app.Activity;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.SurfaceTexture;
import android.os.Bundle;
import android.view.Gravity;
import android.view.TextureView;
import android.widget.FrameLayout;

@SuppressWarnings({"UnusedDeclaration"})
public class CanvasTextureViewActivity extends Activity
        implements TextureView.SurfaceTextureListener {
    private TextureView mTextureView;
    private CanvasTextureViewActivity.RenderingThread mThread;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        FrameLayout content = new FrameLayout(this);

        mTextureView = new TextureView(this);
        mTextureView.setSurfaceTextureListener(this);
        mTextureView.setOpaque(false);

        content.addView(mTextureView, new FrameLayout.LayoutParams(500, 500, Gravity.CENTER));
        setContentView(content);
    }

    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        mThread = new RenderingThread(mTextureView);
        mThread.start();
    }

    @Override
    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
        // Ignored
    }

    @Override
    public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
        if (mThread != null) mThread.stopRendering();
        return true;
    }

    @Override
    public void onSurfaceTextureUpdated(SurfaceTexture surface) {
        // Ignored
    }

    private static class RenderingThread extends Thread {
        private final TextureView mSurface;
        private volatile boolean mRunning = true;

        public RenderingThread(TextureView surface) {
            mSurface = surface;
        }

        @Override
        public void run() {
            float x = 0.0f;
            float y = 0.0f;
            float speedX = 5.0f;
            float speedY = 3.0f;

            Paint paint = new Paint();
            paint.setColor(0xff00ff00);

            while (mRunning && !Thread.interrupted()) {
                final Canvas canvas = mSurface.lockCanvas(null);
                try {
                    canvas.drawColor(0x00000000, PorterDuff.Mode.CLEAR);
                    canvas.drawRect(x, y, x + 20.0f, y + 20.0f, paint);
                } finally {
                    mSurface.unlockCanvasAndPost(canvas);
                }

                if (x + 20.0f + speedX >= mSurface.getWidth() || x + speedX <= 0.0f) {
                    speedX = -speedX;
                }
                if (y + 20.0f + speedY >= mSurface.getHeight() || y + speedY <= 0.0f) {
                    speedY = -speedY;
                }

                x += speedX;
                y += speedY;

                try {
                    Thread.sleep(15);
                } catch (InterruptedException e) {
                    // Interrupted
                }
            }
        }

        void stopRendering() {
            interrupt();
            mRunning = false;
        }
    }
}