原文地址：

下面我们介绍android自定义控件的实现，简单说就是指自己继承原有控件并增加一些方法和属性

首先我们需要在资源文件里定义所需的属性

在res/values下新建attr.xml

内容如下

然后我们定义一个AlphaImageView类，继承ImageView

package com.happyrxk.my;import java.util.Timer;import java.util.TimerTask;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.os.Handler;import android.os.Message;import android.util.AttributeSet;import android.widget.ImageView;public class AlphaImageView extends ImageView{        private int alphaDelta = 0;        private int curAlpha = 0;        private final int SPEED = 300;        private final int CHANGE = 0x110;    Handler handler = new Handler(){        @Override        public void handleMessage(Message msg) {            // TODO Auto-generated method stub            super.handleMessage(msg);            if(msg.what==CHANGE){                curAlpha+=alphaDelta;                if(curAlpha>255){                    curAlpha = 255;                }                AlphaImageView.this.setAlpha(curAlpha);            }        }            };    public AlphaImageView(Context context, AttributeSet attrs) {        super(context, attrs);        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.AlphaImageView);                int duration = typedArray.getInt(R.styleable.AlphaImageView_duration, 0);        alphaDelta = 255 * SPEED /duration;        // TODO Auto-generated constructor stub    }    @Override    protected void onDraw(Canvas canvas) {        // TODO Auto-generated method stub        super.onDraw(canvas);        this.setAlpha(curAlpha);        final Timer timer = new Timer();        timer.schedule(new TimerTask(){            @Override            public void run() {                // TODO Auto-generated method stub                Message msg = new Message();                msg.what = CHANGE;                if(curAlpha>=255){                    timer.cancel();                }else{                    handler.sendMessage(msg);                }                            }                    }, 0, SPEED);    }        }

在我们在xml中用自定义控件是的方法如下