Question

我在本机代码中做了一些位图动画，所以我需要每帧重绘一次ImageView：

class MyImageView extends ImageView
{
    ...

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

似乎一切都很好，除了Traceview显示：

enter image description here

我不了解你，但这似乎有些荒谬。 native_drawStuff（）设置位图的每个像素，然后将位图绘制到画布，而一个简单的invalidate（）调用几乎 4倍？位图也不小（RGBA_8888，从50k到300k像素）。

鉴于我需要每帧重绘整个ImageView，有没有更好的方法呢？我见过的唯一的建议就是只使你需要重绘的视图部分无效，但就我而言，无论如何这都是整个事情。

Answer 1

API 14为此引入了完美的课程：TextureView

TextureView可用于显示内容流。这样的内容流可以例如是视频或OpenGL场景。内容流可以来自应用程序的进程以及远程过程

Romain Guy发布了一个示例，说明如何从另一个线程将内容流式传输到TextureView：https://groups.google.com/forum/#!topic/android-developers/_Ogjc8sozpA。我在这里复制它是为了后人：

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;
        }
    }
}

Answer 2

你不应该在onDraw中调用invalidate（），因为invalidate（）在UI线程上尽快调用onDraw（）。你应该使用postInvalidateDelayed（delayMilliseconds）; （如果您想要间隔刷新视图，或使用不同的Thread或Handler，则不是故意在onDraw（）中）。如果您尝试频繁刷新视图，请使用：

 YourView v;

 //starting refreshing view , prefer to start it in onresume
 Runnable updateRunnable = new Runnable(){
      @Override
      public void run(){
           v.invalidate();
           v.postDelayed(updateRunnable, 1000 / 30);//1000 ms / 30fps
      }
 };
 v.post(updateRunnable);
 ...
 //stopping it
 v.removeCallbacks(updateRunnable);//prefer to do it in onpause

这将以30fps更新您的视图。如果你的表现可以处理它。

View.invalidate（）非常慢。备择方案？

2 个答案: