Android 在列表List中显示半透明小窗体效果的控件

import android.content.Context;
import android.graphics.PixelFormat;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.View;
import android.view.WindowManager;
import android.view.WindowManager.LayoutParams;
import android.widget.TextView;

/**
* 窗口中间显示半透明提示框的小组件
* 用法：1. new 2. showPrevLetter(String prevLetter)
* @author LL
*
*/
public class PrevLetterDialog {
//窗体消失的延时时间
private static final int DELAYED_HIDEN = 500;

// 实现Runnable接口的类
private RemoveWindow mRemoveWindow = new RemoveWindow();
//在Handler里能实现对UI线程的修改
private Handler mHandler;
//窗体管理器
private WindowManager mWindowManager;
//显示在窗体中间半透明的字体框
private TextView mDialogText;
//是否正在显示中
private boolean mShowing;
//是否准备好显示了
private boolean mReady;
//显示在窗体中的字符
private char mPrevLetter = Character.MIN_VALUE;

/**
* 注明：context一定要在可见UI中通过getContext()获得，否则会抛异常。
* @param context
*/
public PrevLetterDialog(Context context) {
//得到窗体管理器
mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);

//得到布部创建者
LayoutInflater inflate = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
//得到TextView
mDialogText = (TextView) inflate.inflate(R.layout.list_position, null);
//设TextView为可见
mDialogText.setVisibility(View.INVISIBLE);

//通过handler把mDialogText展示出来
mHandler = new Handler();
//要用post可实现在多线程里调用UI线程并改变
mHandler.post(new Runnable() {
public void run() {
mReady = true;
//窗体的布局参数
WindowManager.LayoutParams lp = new WindowManager.LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.TYPE_APPLICATION,
WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
PixelFormat.TRANSLUCENT);
//把TextView添加到窗体中去
mWindowManager.addView(mDialogText, lp);
}
});

}

//设置可见性
public void setmReady(boolean mReady) {
this.mReady = mReady;
}

/**
* 一般用在onScroll方法中,参数是字符串，不能为空，会取第一个字符显示
* @param prevLetter
*/
public void showPrevLetter(String prevLetter) {
if (!mReady) {
return;
}
char firstLetter = prevLetter.charAt(0);

if (!mShowing && firstLetter != mPrevLetter) {

mShowing = true;
mDialogText.setVisibility(View.VISIBLE);

}
//设TextView显示的字体
mDialogText.setText(((Character) firstLetter).toString());
//移除mRemoveWindow实现的Runnable接口类
mHandler.removeCallbacks(mRemoveWindow);
//添加mRemoveWindow实现的Runnable接口类，并设延时
mHandler.postDelayed(mRemoveWindow, DELAYED_HIDEN);
mPrevLetter = firstLetter;

}

/**
* 实现Runnable接口的类
*/
private final class RemoveWindow implements Runnable {
public void run() {
removeWindow();
}
}

private void removeWindow() {
if (mShowing) {
mShowing = false;
mDialogText.setVisibility(View.INVISIBLE);
}
}

}

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:textSize="50sp"
android:textColor="@color/band_common_content"
android:background="@drawable/common_list_title"
android:minWidth="70dip"
android:layout_height="wrap_content"
android:padding="5dip"
android:gravity="center"
/>