android 涂鸦与延时问题

来源：互联网发布：办公网络编辑：程序博客网时间：2024/05/20 22:37

最近在做android 涂鸦，采用的是在 FramLayout布局，后面一层加载的是背景图片，前面一层是自定义的view

public class PicEditView extends View {private int screenWidth, screenHeight;// 屏幕長寬private Bitmap mBitmap;private Canvas mCanvas;private Path mPath;private Paint mBitmapPaint;// 画布的画笔private Paint mPaint;// 真实的画笔private float mX, mY;// 临时点坐标private static final float TOUCH_TOLERANCE = 4;public PicEditView(Context context, int w, int h) {this(context, null);screenWidth = w;screenHeight = h;mBitmap = Bitmap.createBitmap(screenWidth, screenHeight,Bitmap.Config.ARGB_8888);mCanvas = new Canvas(mBitmap);mBitmapPaint = new Paint(Paint.DITHER_FLAG);mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setStyle(Paint.Style.STROKE);mPaint.setStrokeJoin(Paint.Join.ROUND);// 设置外边缘mPaint.setStrokeCap(Paint.Cap.SQUARE);// 形状mPaint.setStrokeWidth(5);// 画笔宽度}public void setPaintColor(int color){mPaint.setColor(color);}@Overrideprotected void onAttachedToWindow() {// TODO Auto-generated method stubsuper.onAttachedToWindow();}public PicEditView(Context context, AttributeSet attrs) {super(context, attrs);}@Overrideprotected void onDraw(Canvas canvas) {canvas.drawColor(0x00000000);// 将前面已经画过得显示出来canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);if (mPath != null) {// 实时的显示canvas.drawPath(mPath, mPaint);}super.onDraw(canvas);}private void touch_start(float x, float y) {mPath.moveTo(x, y);mX = x;mY = y;}private void touch_move(float x, float y) {float dx = Math.abs(x - mX);float dy = Math.abs(mY - y);//触摸间隔大于阈值才绘制路径if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {// 从x1,y1到x2,y2画一条贝塞尔曲线，更平滑(直接用mPath.lineTo也是可以的)mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);mX = x;mY = y;}}private void touch_up() {mPath.lineTo(mX, mY);mCanvas.drawPath(mPath, mPaint);}public boolean onTouchEvent(MotionEvent event) {float x = event.getX();float y = event.getY();switch (event.getAction()) {case MotionEvent.ACTION_DOWN:// 每次down下去重新new一个PathmPath = new Path();touch_start(x, y);System.out.println("ACTION_DOWN");this.postInvalidate();//invalidate();break;case MotionEvent.ACTION_MOVE:System.out.println("--MOVE--");touch_move(x, y);this.postInvalidate();//invalidate();break;case MotionEvent.ACTION_UP:touch_up();System.out.println("--ACTION_UP--");this.postInvalidate();//invalidate();break;}return true;}}

然而，在demo上，绘制很实时流畅，整合进代码里，就有很明显的延时与卡顿，对比分析后发现，是由于从相册获取的背景层图片比较大，消耗了内存，导致绘制的延时。

因此在加载图片是，缩小了图片的大小，从而可以流畅的涂鸦。

try {BitmapFactory.Options options = new BitmapFactory.Options();//图片宽高都为原来的二分之一，即图片为原来的四分之一//这样可以避免内存消耗，否则，后面绘图时，会出现很大的延时            options.inSampleSize = 2;//bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageFileUri),null,options);imgView.setImageBitmap(bitmap);//bitmap.recycle();} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}

保存涂鸦结果（底图+涂鸦）：

layout = (FrameLayout) findViewById(R.id.container);DisplayMetrics displayMetrics = getResources().getDisplayMetrics();mView = new MView(this, displayMetrics.widthPixels, displayMetrics.heightPixels - dip2px(this, 40));layout.addView(mView);findViewById(R.id.tSave).setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stublayout.setDrawingCacheEnabled(true);layout.buildDrawingCache();Bitmap b1 = layout.getDrawingCache();//copy 缓存图像 Bitmap b = Bitmap.createBitmap(b1);  layout.destroyDrawingCache();//这个之后，b1 就被 recycle了System.out.println(Environment.getExternalStorageDirectory().getPath() );File file = new File(Environment.getExternalStorageDirectory().getPath() +"/test1.png");savePic(b, file);}});

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