import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Path;import android.view.MotionEvent;import android.view.View;public class GestureView extends View

{private

Paint paint;private

float startX = Float.NaN;private float startY = Float.NaN;private float endX =

Float.NaN;private float endY =

Float.NaN;//下层viewprivate View

viewer;private

static final int gestureColor = Color.rgb(153,

153, 153);private static final int alpha =

220;private static final int alpha_full = 255;//刀锋长度private static final int shape_length = 40;//刀锋截短时间private static final int shape_cut_time = 150;public

GestureView(Context context, View

viewer) {super(context);this.viewer = viewer;

paint = new Paint();

paint.setStyle(Paint.Style.FILL);

}public

void draw(Canvas canvas) {super.draw(canvas);if (!Float.isNaN(startX) &&

!Float.isNaN(endY)) {float gap =

ViewUtils.getGap(startX, startY, endX,

endY);float

w = gap

/ 10;//背景shape外侧点高度float h

= w > 7 ?

7 : w;//填充shape外侧点高度float h2 =

h * 2

/ 3; double

length = Math.pow(Math.pow(w, 2)

+ Math.pow((h), 2),

0.5);double length2 = Math.pow(Math.pow(w, 2)

+ Math.pow((h2), 2),

0.5);double

ang1_1 = Math.atan((endY - startY) / (endX

- startX));double ang1_2 = Math.atan(h / w);double angle1_1 = ang1_1 + ang1_2;double angle1_2 = ang1_1 - ang1_2;double

ang2_2 = Math.atan(h2 / w);double angle2_1 = ang1_1 + ang2_2;double angle2_2 = ang1_1 - ang2_2;if (endX > startX) {float xx1 =

endX - (float)

(length * Math.cos(angle1_1));float yy1 =

endY - (float)

(length * Math.sin(angle1_1));float xx2 =

endX - (float)

(length * Math.cos(angle1_2));float yy2 =

endY - (float)

(length * Math.sin(angle1_2));float xx12 =

endX - (float)

(length2 * Math.cos(angle2_1));float yy12 =

endY - (float)

(length2 * Math.sin(angle2_1));float xx22 =

endX - (float)

(length2 * Math.cos(angle2_2));float yy22 =

endY - (float)

(length2 * Math.sin(angle2_2));

Path backPath =

new Path();

backPath.moveTo(startX, startY);

backPath.lineTo(xx1, yy1);

backPath.lineTo(endX, endY);

backPath.lineTo(xx2, yy2);

backPath.close();

Path fillPath =

new Path();

fillPath.moveTo(startX, startY);

fillPath.lineTo(xx12, yy12);

fillPath.lineTo(endX, endY);

fillPath.lineTo(xx22, yy22);

fillPath.close();

paint.setColor(gestureColor);

paint.setAlpha(alpha);

canvas.drawPath(backPath, paint);

paint.setColor(Color.WHITE);

paint.setAlpha(alpha_full);

canvas.drawPath(fillPath, paint);

} else {float xx1 =

endX + (float)

(length * Math.cos(angle1_1));float yy1 =

endY + (float)

(length * Math.sin(angle1_1));float xx2 =

endX + (float)

(length * Math.cos(angle1_2));float yy2 =

endY + (float)

(length * Math.sin(angle1_2));float xx12 =

endX + (float)

(length2 * Math.cos(angle2_1));float yy12 =

endY + (float)

(length2 * Math.sin(angle2_1));float xx22 =

endX + (float)

(length2 * Math.cos(angle2_2));float yy22 =

endY + (float)

(length2 * Math.sin(angle2_2));

Path backPath =

new Path();

backPath.moveTo(startX, startY);

backPath.lineTo(xx1, yy1);

backPath.lineTo(endX, endY);

backPath.lineTo(xx2, yy2);

backPath.close();

Path fillPath =

new Path();

fillPath.moveTo(startX, startY);

fillPath.lineTo(xx12, yy12);

fillPath.lineTo(endX, endY);

fillPath.lineTo(xx22, yy22);

fillPath.close();

paint.setColor(gestureColor);

paint.setAlpha(alpha);

canvas.drawPath(backPath, paint);

paint.setColor(Color.WHITE);

paint.setAlpha(alpha_full);

canvas.drawPath(fillPath, paint);

}

}

}public

boolean onTouchEvent(android.view.MotionEvent event)

{if(event.getPointerCount() == 1){int action = event.getAction();if (MotionEvent.ACTION_DOWN == action)

{

startX = event.getX();

startY = event.getY();

} else if (MotionEvent.ACTION_MOVE == action)

{

endX = event.getX();

endY = event.getY();//刀锋截短时间，则截短至一半if ((event.getEventTime() - event.getDownTime()) > shape_cut_time) {if(Math.abs(endX - startX) > shape_length &&

Math.abs(endY - startY) > shape_length){

startX = (float)

(startX + (endX -

startX) * 0.5);

startY = (float)

(startY + (endY -

startY) * 0.5);

}

}

invalidate();

} else if (MotionEvent.ACTION_UP == action)

{

startX = Float.NaN;

startY = Float.NaN;

endX = Float.NaN;

endY = Float.NaN;

invalidate();

}

}//该view消费了event，所以下层的view必须dispatchTouchEvent才能获得事件MotionEvent newEvent

= MotionEvent.obtain(event);

viewer.dispatchTouchEvent(newEvent);return true;

}

}