Android开发之跟随手指的小球

想要实现一个应用，界面上有一个小球，能够跟随手指的移动而移动。这需要自定义UI：

public class DrawView extends View{

public DrawView(Context context) {

super(context);

// TODO Auto-generated constructor stub

}

public floatcurrentX = 40;

public floatcurrentY = 50;

public void onDraw(Canvas canvas){

super.onDraw(canvas);

//创建画笔

Paint p = new Paint();

//设置画笔的颜色

p.setColor(Color.RED);

//绘制一个小圆（作为小球）

canvas.drawCircle(currentX,currentY, 15, p);

}

}

接下来是mainactivity.java：

public class MainActivity extends Activity {


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//获取布局文件中的LinearLayout容器
LinearLayout root = (LinearLayout)findViewById(R.id.root);
//创建DrawView组件
final DrawView draw = new DrawView(this);
//设置自定义组件的最大宽度、高度
draw.setMinimumHeight(500);
draw.setMinimumWidth(300);
//为draw组件绑定Touch事件
draw.setOnTouchListener(new OnTouchListener() {

@Override
public boolean onTouch(View arg0, MotionEvent event) {
//修改draw组件的currentX、currentY两个属性
draw.currentX = event.getX();
draw.currentY = event.getY();
//通知draw组件重绘
draw.invalidate();
//返回true表明处理方法已经处理该事件
return true;
}
});
root.addView(draw);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}


}

Run and have fun！