Android贝塞尔曲线实现手指轨迹

public class MyView extends View { // 实例一个路径对象 private Path mPath = new Path(); public MyView(Context context) {  super(context);  // TODO Auto-generated constructor stub } public MyView(Context context, AttributeSet attrs) {  super(context, attrs); } @Override public boolean onTouchEvent(MotionEvent event) {  // TODO Auto-generated method stub  switch (event.getAction()) {  // 按下  case MotionEvent.ACTION_DOWN:   //getX()和getY()获得的永远是相对view的触摸位置坐标   mPath.moveTo(event.getX(), event.getY());   // return true表示当前控件已经消费了下按动作，   // 之后的ACTION_MOVE、ACTION_UP动作也会继续传递到当前控件中   return true;   // 移动  case MotionEvent.ACTION_MOVE:   mPath.lineTo(event.getX(), event.getY());   // postInvalidate用来重绘控件,在非UI线程中使用   postInvalidate();  default:   break;  }  return super.onTouchEvent(event); } @Override protected void onDraw(Canvas canvas) {  // TODO Auto-generated method stub  super.onDraw(canvas);  // 实例一个画笔并设置画笔样式  Paint paint = new Paint();  paint.setColor(Color.RED);  paint.setStyle(Paint.Style.STROKE);// 填充样式改为描边  // 路径和画笔联合绘制成图形  canvas.drawPath(mPath, paint); } public void reset() {  // 清除掉path里的线条和曲线，但是不会改变它的fill－type  mPath.reset();  //刷新View,清屏  invalidate(); }}

public class MyActivity extends Activity { MyView myView; Button reset; @Override protected void onCreate(Bundle savedInstanceState) {  // TODO Auto-generated method stub  super.onCreate(savedInstanceState);  setContentView(R.layout.gesture);  myView = (MyView) findViewById(R.id.myView);  reset = (Button) findViewById(R.id.reset);  reset.setOnClickListener(new OnClickListener() {   @Override   public void onClick(View v) {    // TODO Auto-generated method stub    myView.reset();   }  }); }}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <Button  android:id="@+id/reset"  android:layout_width="match_parent"  android:layout_height="wrap_content"  android:text="reset" /> <com.example.gesture.MyView  android:id="@+id/myView"  android:layout_width="match_parent"  android:layout_height="match_parent" /></LinearLayout>

public class MySecondView extends View { private Path mPath=new Path(); private float mPreX,mPreY; public MySecondView(Context context) {  super(context); } public MySecondView(Context context, AttributeSet attrs) {  super(context, attrs);  // TODO Auto-generated constructor stub } @Override public boolean onTouchEvent(MotionEvent event) {  // TODO Auto-generated method stub  switch (event.getAction()) {  case MotionEvent.ACTION_DOWN:   //将Path的初始位置设置到手指的触点处    mPath.moveTo(event.getX(), event.getY());    mPreX=event.getX();    mPreY=event.getY();    return true;  case MotionEvent.ACTION_MOVE:   float endX=(mPreX+event.getX())/2;   float endY=(mPreY+event.getY())/2;   //quadTo前两个参数是控制点，后两个是终点   mPath.quadTo(mPreX, mPreY, endX, endY);   mPreX=event.getX();   mPreY=event.getY();   invalidate();  default:   break;  }  return super.onTouchEvent(event); }  @Override   protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    Paint paint = new Paint();    paint.setStyle(Paint.Style.STROKE);    paint.setColor(Color.RED);    paint.setStrokeWidth(2);    canvas.drawPath(mPath,paint);   }   public void reset(){    mPath.reset();    postInvalidate();   } }