android光滑绘图可变宽度笔

要绘制代码 path 使用可变的描边宽度

public class FingerPaint extends GraphicsActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(new MyView(this));}public void colorChanged(int color)  {}public class MyView extends View {private static final float STROKE_WIDTH = 5f;    private Paint paint = new Paint();private Path mPath = new Path();ArrayList<Path> mPaths = new ArrayList<Path>();ArrayList<Integer> mStrokes = new ArrayList<Integer>();private float lastTouchX;private float lastTouchY;private final RectF dirtyRect = new RectF();private int lastStroke = -1;int variableWidthDelta = 0;private static final float STROKE_DELTA = 0.0001f; // for float comparisonprivate static final float STROKE_INCREMENT = 0.01f; // amount to interpolateprivate float currentStroke = STROKE_WIDTH;private float targetStroke = STROKE_WIDTH;private float mX, mY;private static final float TOUCH_TOLERANCE = 4;public MyView(Context context)  {super(context);paint.setAntiAlias(true);paint.setDither(true);paint.setStyle(Paint.Style.STROKE);paint.setStrokeJoin(Paint.Join.ROUND);paint.setStrokeCap(Paint.Cap.ROUND);    paint.setStrokeWidth(STROKE_WIDTH);}public void clear() {mPath.reset();// Repaints the entire view.invalidate();}@Overrideprotected void onDraw(Canvas canvas)  {for(int i=0; i<mPaths.size();i++) {paint.setStrokeWidth(mStrokes.get(i));canvas.drawPath(mPaths.get(i), paint);}}@Overridepublic boolean onTouchEvent(MotionEvent event) {float eventX = event.getX();float eventY = event.getY();int historySize = event.getHistorySize();switch (event.getAction()) {case MotionEvent.ACTION_DOWN: {resetDirtyRect(eventX, eventY);
//                  mPath.reset();mPath.moveTo(eventX, eventY);mX = eventX;mY = eventY;break;                  }case MotionEvent.ACTION_MOVE: {                 if (event.getPressure()>=0.00 && event.getPressure()<0.05) {variableWidthDelta = -2;} else if (event.getPressure()>=0.05 && event.getPressure()<0.10) {variableWidthDelta = -2;} else if (event.getPressure()>=0.10 && event.getPressure()<0.15) {variableWidthDelta = -2;} else if (event.getPressure()>=0.15 && event.getPressure()<0.20) {variableWidthDelta = -2;} else if (event.getPressure()>=0.20 && event.getPressure()<0.25) {variableWidthDelta = -2;} else if (event.getPressure() >= 0.25 && event.getPressure()<0.30) {variableWidthDelta = 1;} else if (event.getPressure() >= 0.30 && event.getPressure()<0.35) {variableWidthDelta = 2;} else if (event.getPressure() >= 0.35 && event.getPressure()<0.40) {variableWidthDelta = 3;} else if (event.getPressure() >= 0.40 && event.getPressure()<0.45) {variableWidthDelta = 4;} else if (event.getPressure() >= 0.45 && event.getPressure()<0.60) {variableWidthDelta = 5;}                                          // if current not roughly equal to targetif( Math.abs(targetStroke - currentStroke) > STROKE_DELTA ) {// move towards target by the incrementif( targetStroke > currentStroke){currentStroke = Math.min(targetStroke, currentStroke + STROKE_INCREMENT);}else{currentStroke = Math.max(targetStroke, currentStroke - STROKE_INCREMENT);}} mStrokes.add((int) currentStroke);targetStroke = variableWidthDelta;float dx = Math.abs(eventX - mX);float dy = Math.abs(eventY - mY);if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {if(lastStroke != variableWidthDelta) {mPath.lineTo(mX, mY);mPath = new Path();mPath.moveTo(mX,mY);mPaths.add(mPath);}mPath.quadTo(mX, mY, (eventX + mX)/2, (eventY + mY)/2);mX = eventX;mY = eventY;}for (int i = 0; i < historySize; i++) {float historicalX = event.getHistoricalX(i);float historicalY = event.getHistoricalY(i);expandDirtyRect(historicalX, historicalY);}break;}case MotionEvent.ACTION_UP: {for (int i = 0; i < historySize; i++) {float historicalX = event.getHistoricalX(i);float historicalY = event.getHistoricalY(i);expandDirtyRect(historicalX, historicalY);}mPath.lineTo(mX, mY);                   break;}}// Include half the stroke width to avoid clipping.invalidate();lastTouchX = eventX;lastTouchY = eventY;lastStroke = variableWidthDelta;return true;}private void expandDirtyRect(float historicalX, float historicalY) {if (historicalX < dirtyRect.left) {dirtyRect.left = historicalX;}  else if (historicalX > dirtyRect.right) {dirtyRect.right = historicalX;}if (historicalY < dirtyRect.top) {dirtyRect.top = historicalY;} else if (historicalY > dirtyRect.bottom) {dirtyRect.bottom = historicalY;}}/*** Resets the dirty region when the motion event occurs.*/private void resetDirtyRect(float eventX, float eventY) {// The lastTouchX and lastTouchY were set when the ACTION_DOWN// motion event occurred.dirtyRect.left = Math.min(lastTouchX, eventX);dirtyRect.right = Math.max(lastTouchX, eventX);dirtyRect.top = Math.min(lastTouchY, eventY);dirtyRect.bottom = Math.max(lastTouchY, eventY);}}
}

我得到的输出结果

我想要实现的输出

而不是立即跳到新的描边宽度，当你发现转变了，你可以设定一个目标和插值朝它，直到你到达它。你 mStrokes 将需要Float 而不是 s Integer s。

private static final float STROKE_DELTA = 0.0001f; // for float comparison
private static final float STROKE_INCREMENT = 0.01f; // amount to interpolate
private float currentStroke = STROKE_WIDTH;
private float targetStroke = STROKE_WIDTH;

在那里你目前正在创建新的 path 为一个新的描边宽度，做这样的事情：

// if current not roughly equal to target
if( Math.abs(targetStroke - currentStroke) > STROKE_DELTA ) {// move towards target by the incrementif( targetStroke > currentStroke )currentStroke = Math.min(targetStroke, currentStroke + STROKE_INCREMENT);elsecurrentStroke = Math.max(targetStroke, currentStroke - STROKE_INCREMENT);mPath.lineTo(mX, mY);mPath = new Path();mPath.moveTo(mX,mY);mPaths.add(mPath);mStrokes.add(currentStroke);
}

您将更新 targetStroke 在哪里你当前设置 variableWidthDelta