跟随手指的小球

    

 

Crize_demo\draw_demo\src\main\java\com\ly\draw_demo\DrawView.java

 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     @Override

17     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 }

 

Crize_demo\draw_demo\src\main\res\layout\activity_main.xml

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>

 

Crize_demo\draw_demo\src\main\java\com\ly\draw_demo\MainActivity.java

 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     @Override

10     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             @Override

23             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 }