public class MyView extends View {

 // 實例一個路徑對象
 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()獲得的永遠是相對view的觸摸位置坐標
   mPath.moveTo(event.getX(), event.getY());
   // return true表示當前控件已經(jīng)消費了下按動作，
   // 之后的ACTION_MOVE、ACTION_UP動作也會繼續(xù)傳遞到當前控件中
   return true;
   // 移動
  case MotionEvent.ACTION_MOVE:
   mPath.lineTo(event.getX(), event.getY());
   // postInvalidate用來重繪控件,在非UI線程中使用
   postInvalidate();
  default:
   break;
  }
  return super.onTouchEvent(event);
 }

 @Override
 protected void onDraw(Canvas canvas) {
  // TODO Auto-generated method stub
  super.onDraw(canvas);
  // 實例一個畫筆并設置畫筆樣式
  Paint paint = new Paint();
  paint.setColor(Color.RED);
  paint.setStyle(Paint.Style.STROKE);// 填充樣式改為描邊
  // 路徑和畫筆聯(lián)合繪制成圖形
  canvas.drawPath(mPath, paint);
 }

 public void reset() {
  // 清除掉path里的線條和曲線，但是不會改變它的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:
   //將Path的初始位置設置到手指的觸點處
    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前兩個參數(shù)是控制點，后兩個是終點
   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(); 
  } 

}