首先自定义一个View子类:

package com.example.androidtest0.myView;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class DrawView extends View {
	public float currentX = 40;
	public float currentY = 50;
	//定义、并创建画笔
	Paint p = new Paint();
	public DrawView(Context context) {
		super(context);
	}

	public DrawView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}
	
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		//设置画笔的颜色
		p.setColor(Color.RED);
		//绘制一个小球
		canvas.drawCircle(currentX, currentY, 15, p);
	}
	
	/**
	 * 为该组件的触碰事件重写事件处理方法
	 */
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		//修改currentX、currentY两个属性
		currentX = event.getX();
		currentY = event.getY();
		//通知当前组件重绘自己
		invalidate();
		return true;
	}
	
    
	

}

custom_layout.xml

<pre name="code" class="java"><?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:id="@+id/root"
    android:orientation="vertical" >

</LinearLayout>

主activity:

package com.example.androidtest0;

import com.example.androidtest0.myView.DrawView;

import android.app.Activity;
import android.os.Bundle;
import android.widget.LinearLayout;

public class CustomView extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.custom_layout);
		//获取布局文件中LinearLayout容器
		LinearLayout root = (LinearLayout)findViewById(R.id.root);
		//创建DrawView组件
		final DrawView drawView = new DrawView(this);
		//设置自定义组件的最小宽度、高度
		drawView.setMinimumWidth(10);
		drawView.setMinimumHeight(10);
		root.addView(drawView);
	}
}

除此之外：

还可以用XML的方式：也是首先建一个View的子类，和上面一样。然后主界面XML如下：

<?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:id="@+id/root"
    android:orientation="vertical" >

    <com.example.androidtest0.myView.DrawView 
        android:layout_width="match_parent" android:layout_height="match_parent"
        />
</LinearLayout>

package com.example.androidtest0;

import com.example.androidtest0.myView.DrawView;

import android.app.Activity;
import android.os.Bundle;
import android.widget.LinearLayout;

public class CustomView extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.custom_layout);
	}
}

android 自定义组件随着手指自动画圆