建立android畫筆程式的例子(有鏡面效果)

標籤：android手指畫   鏡面效果   

先：

關鍵是在檢測到手指移動的時候用mPath.quadTo的方法，android sdk解釋是:

Add a quadratic bezier from the last point, approaching control point (x1,y1), and ending at (x2,y2). If no moveTo() call has been made for this contour, the first point is automatically set to (0,0).

中文是用貝茲路徑連結了(x1,y1),(x2,y2)這兩個點，如果沒有moveTo()這個方法調用的話，第一個點預設為(0,0)

android畫圖是用Canvas的API,如畫一個實心的矩形，可以用在重寫一個View的onDraw():

<span style="white-space:pre"></span>Rect rect = new Rect(100,100,500,500);mPaint.setStrokeWidth(5); //設定畫筆的粗細mPaint.setColor(Color.RED); //設定畫筆的顏色mPaint.setStyle(Style.FILL); //填充整個圖形mPaint.setAntiAlias(true); //消除鋸齒效果canvas.drawRect(rect, mPaint);

對於檢測手指的移動，我們可以用onTouchEvent來實現:

private float mX, mY;private float mOppositeX, mOppositeY;private static final float TOUCH_TOLERANCE = 4; //當手指移動超過4時我們才去set Path@Overridepublic boolean onTouchEvent(MotionEvent event) {float x = event.getX();float y = event.getY();switch (event.getAction()) {case MotionEvent.ACTION_DOWN:touch_start(x, y);if(isMirrorDraw) {touch_opposite_start(x, y);}invalidate();break;case MotionEvent.ACTION_MOVE:touch_move(x, y);if(isMirrorDraw) {touch_opposite_move(x, y);}invalidate();break;case MotionEvent.ACTION_UP:touch_up();if(isMirrorDraw) {touch_opposite_up();}invalidate();break;}return true;}private void touch_start(float x, float y) {mPath.reset();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(y - mY);if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {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);mPath.reset();}private void touch_opposite_up() {mOppositePath.lineTo(mOppositeX, mY);mCanvas.drawPath(mOppositePath, mOppoPaint);mOppositePath.reset();}private void touch_opposite_move(float x, float y) {float oppositeX = OppositeDrawActivity.screenWidth - x; //<span style="font-family: Arial, Helvetica, sans-serif;">OppositeDrawActivity.screenWidth是螢幕寬度</span>float dx = Math.abs(oppositeX - mOppositeX);float dy = Math.abs(y - mY);if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {mOppositePath.quadTo(mOppositeX, mY, (mOppositeX + oppositeX) / 2, (y + mY) / 2);mOppositeX = oppositeX;mY = y;}}private void touch_opposite_start(float x, float y) {mOppositePath.reset();float oppositeX = OppositeDrawActivity.screenWidth - x;mOppositePath.moveTo(oppositeX, y);mOppositeX = oppositeX;}

然後重寫onDraw():

@Overrideprotected void onDraw(Canvas canvas) {canvas.drawColor(0xFFAAAAAA);canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);canvas.drawPath(mPath, mPaint);if(isMirrorDraw) {canvas.drawPath(mOppositePath, mOppoPaint);}}

代碼可以在http://download.csdn.net/detail/baidu_nod/7572549下載