Android实现在列表List中显示半透明小窗体效果的控件用法详解

import com.hiapk.market.R;
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"
/>