Android快速像素操作

Question

我正在尝试编写一些代码，让我在屏幕上绘制像素数组。然而，我在 Arm cortex A8 600mhz、320x240 像素下的性能非常糟糕。

有人可以向我解释瓶颈在哪里和/或如何解决它吗？改变高度和宽度也几乎没有帮助。我注意到 Java 中的 Swing 有类似的行为。我正在使用下面的代码：

package com.pixeldraw;


import java.util.ArrayList;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Debug;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.Window;

public class MainActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(new Panel(this));
        Debug.startMethodTracing("pixeldraw");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Debug.stopMethodTracing();
    }

    class Panel extends SurfaceView implements SurfaceHolder.Callback {
        private TutorialThread _thread;
        private Bitmap _buffer;
        private ArrayList<GraphicObject> _graphics = new ArrayList<GraphicObject>();
        private int width = 40;
        private int height = 40;
        public Panel(Context context) {
            super(context);
            getHolder().addCallback(this);
            _thread = new TutorialThread(getHolder(), this);
            setFocusable(true);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            synchronized (_thread.getSurfaceHolder()) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    GraphicObject graphic = new GraphicObject(BitmapFactory.decodeResource(getResources(), R.drawable.icon));
                    graphic.getCoordinates().setX((int) event.getX() - graphic.getGraphic().getWidth() / 2);
                    graphic.getCoordinates().setY((int) event.getY() - graphic.getGraphic().getHeight() / 2);
                    _graphics.add(graphic);
                }
                return true;
            }
        }
        long lastTime = System.currentTimeMillis();
        int CLOCKS_PER_SEC = 500;
        float timeCnt = 0;
        @Override
        public void onDraw(Canvas canvas) {
            canvas.drawColor(Color.BLACK);
            width = getWidth()/2;
            height = getHeight()/2;

            long frameTime = System.currentTimeMillis();

            // The elapsed seconds per frame will almost always be less than 1.0.
            float elapsedSeconds = (float)(frameTime - lastTime) / CLOCKS_PER_SEC;

            int colors[] = new int[width*height];
            for (int x = 0; x<width ; x++) {
                for (int y = 0; y<height ; y++){
                    int r = (int)(timeCnt/5*255);
                    int b = 0;
                    int g = 0;
                    int a = 255;
                    colors[x + y * width] = (a << 24) | (r << 16) | (g << 8) | b;
                }
            }
            for (int x = 0; x<10 ; x++) {
                for (int y = 0; y<10; y++){
                    int r = 0;
                    int b = 255;
                    int g = 0;
                    int a = 255;
                    colors[(int)(timeCnt*32)+x + y * width] = (a << 24) | (r << 16) | (g << 8) | b;
                }
            }
            _buffer = Bitmap.createBitmap(colors, width, height, Bitmap.Config.RGB_565);
            canvas.drawBitmap(_buffer, 0, 0, null);

            timeCnt += elapsedSeconds;
            if (timeCnt > 5) timeCnt = 0;
            // Update the last time counter so that we can use it next frame.
            lastTime = frameTime;

        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            // TODO Auto-generated method stub
        }

        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            _thread.setRunning(true);
            _thread.start();
        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            // simply copied from sample application LunarLander:
            // we have to tell thread to shut down & wait for it to finish, or else
            // it might touch the Surface after we return and explode
            boolean retry = true;
            _thread.setRunning(false);
            while (retry) {
                try {
                    _thread.join();
                    retry = false;
                } catch (InterruptedException e) {
                    // we will try it again and again...
                }
            }
        }
    }

    class TutorialThread extends Thread {
        private SurfaceHolder _surfaceHolder;
        private Panel _panel;
        private boolean _run = false;

        public TutorialThread(SurfaceHolder surfaceHolder, Panel panel) {
            _surfaceHolder = surfaceHolder;
            _panel = panel;
        }

        public void setRunning(boolean run) {
            _run = run;
        }

        public SurfaceHolder getSurfaceHolder() {
            return _surfaceHolder;
        }

        @Override
        public void run() {
            Canvas c;
            while (_run) {
                c = null;
                try {
                    c = _surfaceHolder.lockCanvas(null);
                    synchronized (_surfaceHolder) {
                        _panel.onDraw(c);
                    }
                } finally {
                    // do this in a finally so that if an exception is thrown
                    // during the above, we don't leave the Surface in an
                    // inconsistent state
                    if (c != null) {
                        _surfaceHolder.unlockCanvasAndPost(c);
                    }
                }
            }
        }
    }

    class GraphicObject {
        /**
         * Contains the coordinates of the graphic.
         */
        public class Coordinates {
            private int _x = 100;
            private int _y = 0;

            public int getX() {
                return _x + _bitmap.getWidth() / 2;
            }

            public void setX(int value) {
                _x = value - _bitmap.getWidth() / 2;
            }

            public int getY() {
                return _y + _bitmap.getHeight() / 2;
            }

            public void setY(int value) {
                _y = value - _bitmap.getHeight() / 2;
            }

            public String toString() {
                return "Coordinates: (" + _x + "/" + _y + ")";
            }
        }

        private Bitmap _bitmap;
        private Coordinates _coordinates;

        public GraphicObject(Bitmap bitmap) {
            _bitmap = bitmap;
            _coordinates = new Coordinates();
        }

        public Bitmap getGraphic() {
            return _bitmap;
        }

        public Coordinates getCoordinates() {
            return _coordinates;
        }
    }
}

Answer 1

根据我们公司的经验 - 在 Android 上，近全屏位图上的逐像素操作非常慢。我们对某种自定义动画进行的最慢的操作之一是通过drawColor()将背景设为黑色，这正是逐像素填充屏幕......

所以在你的情况下，罪魁祸首可能是

   canvas.drawColor(Color.BLACK);

但确实- 进行分析，你就会知道。通过分析，您可以深入了解 onDraw 并查看哪个方法花费最多时间。我们就是这样发现的。

Answer 2

1. 准确...告诉一些数字，而不是非常糟糕

2. 移动昂贵的绘图代码之外的操作

   int 颜色[] = new int[宽度*高度];
   _buffer = Bitmap.createBitmap(colors, width, height, Bitmap.Config.RGB_565);

3. 使用分析http://developer.android.com/guide/ Development/debugging/debugging-tracing.html