追随手指的小球

 1 import android.content.Context; 2 import android.graphics.Canvas; 3 import android.graphics.Color; 4 import android.graphics.Paint; 5 import android.view.View; 6  7 public class DrawView extends View { 8  9     public float currentX = 40;10     public float currentY = 50;11 12     public DrawView(Context context) {13         super(context);14     }15 16     @Override17     protected void onDraw(Canvas canvas) {18         super.onDraw(canvas);19         //创建画笔20         Paint paint = new Paint();21         //设置画笔的颜色22         paint.setColor(Color.RED);23         //绘制一个小圆(作为小球)24         canvas.drawCircle(currentX,currentY,15,paint);25     }26 }

1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"2     xmlns:tools="http://schemas.android.com/tools"3     android:layout_width="match_parent"4     android:layout_height="match_parent"5     android:orientation="horizontal"6     android:id="@+id/root"7     tools:context=".MainActivity">8 9 </LinearLayout>

 1 import android.app.Activity; 2 import android.os.Bundle; 3 import android.view.MotionEvent; 4 import android.view.View; 5 import android.widget.LinearLayout; 6  7 public class MainActivity extends Activity { 8      9     @Override10     protected void onCreate(Bundle savedInstanceState) {11         super.onCreate(savedInstanceState);12         setContentView(R.layout.activity_main);13         //获取布局文件中的LinearLayout容器14         LinearLayout root = (LinearLayout) findViewById(R.id.root);15         //创建DrawView组件16         final DrawView drawView = new DrawView(this);17         //设置自定义框架的宽度和高度18         drawView.setMinimumWidth(300);19         drawView.setMinimumHeight(500);20         //为drawView绑定Touch事件(触摸屏幕的监听事件)21         drawView.setOnTouchListener(new View.OnTouchListener() {22             @Override23             public boolean onTouch(View v, MotionEvent event) {24                 //修改drawView组件的currentX,currentY两个属性25                 drawView.currentX = event.getX();26                 drawView.currentY = event.getY();27                 //通知drawView组件重绘28                 drawView.invalidate();29                 //返回true表明处理方法已经处理该事件30                 return true;31             }32         });33         root.addView(drawView);34     }35 36 37 }