Android 使用自定义组件和自定义属性

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <!-- 定义一个属性 -->
    <attr name="duration"></attr>
    <!-- 定义一个styleable对象来组合多个属性 -->
    <declare-styleable name="AlphaImageView">
        <attr name="duration" />
    </declare-styleable>

</resources>

public class AlphaImageView extends ImageView {

  // 图像透明度每次改变的大小
  private int alphaDelta = 0;
  // 记录图片当前的透明度
  private int CurAlpha = 0;
  // 间隔每隔多少毫秒透明度改变一次
  private final int SPEED = 300;

  Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      switch (msg.what) {
      case 0x11:
        CurAlpha += alphaDelta;
        if (CurAlpha >= 255)
          CurAlpha = 255;
        // 修改透明度
        AlphaImageView.this.setAlpha(CurAlpha);
        break;

      default:
        break;
      }
    }

  };

  public AlphaImageView(Context context, AttributeSet attrs) {
    super(context, attrs);
    // TODO Auto-generated constructor stub

    TypedArray typedArray = context.obtainStyledAttributes(attrs,
        R.styleable.AlphaImageView);
    // 获取duration参数
    int duration = typedArray
        .getInt(R.styleable.AlphaImageView_duration, 0);
    // 计算图像每次改变的大小
    alphaDelta = 255 * SPEED / duration;
  }

  @Override
  protected void onDraw(Canvas canvas) {
    this.setAlpha(CurAlpha);
    super.onDraw(canvas);
    final Timer timer = new Timer();
    timer.schedule(new TimerTask() {

      @Override
      public void run() {
        // TODO Auto-generated method stub
        Message msg = Message.obtain();
        msg.what = 0x11;
        if (CurAlpha >= 255) {
          timer.cancel();
        } else {
          handler.sendMessage(msg);
        }
      }
    }, 0, SPEED);
  }
}

    xmlns:tools="http://schemas.android.com/tools"
    xmlns:crazyit="http://schemas.android.com/apk/res/com.attributexmldemo"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <com.attributexmldemo.AlphaImageView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:src="@drawable/icon1"
        crazyit:duration="60000" />