Android使用贝塞尔曲线仿QQ聊天消息气泡拖拽效果

本文实例为大家分享了Android仿QQ聊天消息气泡拖拽效果展示的具体代码，供大家参考，具体内容如下

先画圆，都会吧。代码如下：

public class Bezier extends View {
 private final Paint mGesturePaint = new Paint();
 private final Path mPath = new Path();
 private float mX1 = 100, mY1 = 150;
 private float mX2 = 300, mY2 = 150;
 private boolean mBezier = true;
 private int mRadius = 30;

 public Bezier(Context context, AttributeSet attrs) {
 super(context, attrs);
 mGesturePaint.setAntiAlias(true);
 mGesturePaint.setStyle(Paint.Style.FILL_AND_STROKE);
 mGesturePaint.setStrokeWidth(5);
 mGesturePaint.setColor(Color.RED);
 }

 @Override
 protected void onDraw(Canvas canvas) {
 // TODO Auto-generated method stub
 super.onDraw(canvas);
 canvas.drawCircle(mX1, mX2, mRadius, mGesturePaint);
 }

}

效果

拖拽的另个一圆就不画了，效果的实现主要是计算两个点之间的拖拽区域，如下图：

求出区域之后，使用贝塞尔线画出效果就可以了，代码：

public class Bezier extends View {
 private final Paint mGesturePaint = new Paint();
 private final Path mPath = new Path();
 private float mX1 = 100, mY1 = 150;
 private float mX2 = 300, mY2 = 150;
 private boolean mBezier = true;
 private int mRadius = 30;

 public Bezier(Context context, AttributeSet attrs) {
 super(context, attrs);
 mGesturePaint.setAntiAlias(true);
 mGesturePaint.setStyle(Paint.Style.FILL_AND_STROKE);
 mGesturePaint.setStrokeWidth(5);
 mGesturePaint.setColor(Color.RED);
 setBezier();
 }

 private void setBezier() {
 float offsetX = (float) (mRadius * Math.sin(Math.atan((mY2 - mY1) / (mX2 - mX1))));
 float offsetY = (float) (mRadius * Math.cos(Math.atan((mY2 - mY1) / (mX2 - mX1))));
 float x1 = mX1 - offsetX;
 float y1 = mY1 + offsetY;

 float x2 = mX2 - offsetX;
 float y2 = mY2 + offsetY;

 float x3 = mX2 + offsetX;
 float y3 = mY2 - offsetY;

 float x4 = mX1 + offsetX;
 float y4 = mY1 - offsetY;

 mPath.reset();
 mPath.moveTo(x1, y1);
 mPath.quadTo((mX1 + mX2) / 2, (mY1 + mY2) / 2, x2, y2);//锚点直接取偏移量的一半
 mPath.lineTo(x3, y3);
 mPath.quadTo((mX1 + mX2) / 2, (mY1 + mY2) / 2, x4, y4);
 mPath.lineTo(x1, y1);
 }

 @Override
 protected void onDraw(Canvas canvas) {
 // TODO Auto-generated method stub
 super.onDraw(canvas);
 //通过画布绘制多点形成的图形
 canvas.drawCircle(mX1, mY1, mRadius, mGesturePaint);
 if (mBezier) {
 canvas.drawPath(mPath, mGesturePaint);
 canvas.drawCircle(mX2, mY2, mRadius, mGesturePaint);
 }
 }
}

效果图：

拖拽效果只要在onTouchEvent里动态改变拖动点的坐标重绘就可以实现了，代码：

public class Bezier extends View {
 private final Paint mGesturePaint = new Paint();
 private final Path mPath = new Path();
 private float mX1 = 100, mY1 = 150;
 private float mX2 = 300, mY2 = 150;
 private boolean mBezier = true;
 private int mRadius = 30;

 public Bezier(Context context, AttributeSet attrs) {
 super(context, attrs);
 mGesturePaint.setAntiAlias(true);
 mGesturePaint.setStyle(Paint.Style.FILL_AND_STROKE);
 mGesturePaint.setStrokeWidth(5);
 mGesturePaint.setColor(Color.RED);
 setBezier();
 }

 private void setBezier() {
 float offsetX = (float) (mRadius * Math.sin(Math.atan((mY2 - mY1) / (mX2 - mX1))));
 float offsetY = (float) (mRadius * Math.cos(Math.atan((mY2 - mY1) / (mX2 - mX1))));
 float x1 = mX1 - offsetX;
 float y1 = mY1 + offsetY;

 float x2 = mX2 - offsetX;
 float y2 = mY2 + offsetY;

 float x3 = mX2 + offsetX;
 float y3 = mY2 - offsetY;

 float x4 = mX1 + offsetX;
 float y4 = mY1 - offsetY;

 mPath.reset();
 mPath.moveTo(x1, y1);
 mPath.quadTo((mX1 + mX2) / 2, (mY1 + mY2) / 2, x2, y2);//锚点直接取偏移量的一半
 mPath.lineTo(x3, y3);
 mPath.quadTo((mX1 + mX2) / 2, (mY1 + mY2) / 2, x4, y4);
 mPath.lineTo(x1, y1);
 }

 @Override
 protected void onDraw(Canvas canvas) {
 // TODO Auto-generated method stub
 super.onDraw(canvas);
 //通过画布绘制多点形成的图形
 canvas.drawCircle(mX1, mY1, mRadius, mGesturePaint);
 if (mBezier) {
 canvas.drawPath(mPath, mGesturePaint);
 canvas.drawCircle(mX2, mY2, mRadius, mGesturePaint);
 }
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {
 mX2 = event.getX();
 mY2 = event.getY();
 switch (event.getAction()) {
 case MotionEvent.ACTION_DOWN:
 mBezier = true;
 setBezier();
 break;
 case MotionEvent.ACTION_MOVE:
 mBezier = true;
 setBezier();
 break;
 case MotionEvent.ACTION_UP:
 mBezier = false;
 break;

 }
 invalidate();
 return true;
 }

}

源码：Android仿QQ聊天消息气泡拖拽效果

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