我正在关注 API Demos 中的“FingerPaint”演示。
我需要获得“喷枪”效果，因为当我在同一个地方画画时，它会变得越来越暗。
请看图片：
正如你所看到的，中心更暗，因为我在同一个地方多次通过油漆。
请问我如何获得相同的效果，如果超过一次绘制会使斑点变暗？
编辑 编辑 编辑
建议的
mPaint.setAlpha(0x80)
一种工作，但只有当我释放触摸然后再次触摸时，如果我不释放并保持手指在屏幕上，则无法达到效果。
关键是，如果您不从屏幕上松开手指，您就不会达到效果，如果您在不松开触摸的情况下继续绘画，则绘画结束时它不会变暗。如果您释放触摸然后再次绘制，您将获得效果
这是我得到的结果。我不想：
这将是期望的结果：
这是取自 API Demos 的代码：
public class FingerPaint extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new MyView(this));
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0x44FF0000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(12);
}
private Paint mPaint;
public class MyView extends View {
private static final float MINP = 0.25f;
private static final float MAXP = 0.75f;
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
public MyView(Context c) {
super(c);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(0xFFAAAAAA);
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
canvas.drawPath(mPath, mPaint);
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
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);
// commit the path to our offscreen
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
mPath.reset();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
}
}
