怎么在Android应用中实现一个查看内存使用情况功能

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
 package="com.itheima28.memorydemo"
 android:versionCode="1"
 android:versionName="1.0" >
 
 <uses-sdk
  android:minSdkVersion="8"
  android:targetSdkVersion="19" />
    
 <application
  android:allowBackup="true"
  android:icon="@drawable/ic_launcher"
  android:label="@string/app_name"
  android:theme="@style/AppTheme" >
  <activity
   android:name="com.itheima28.memorydemo.MainActivity"
   android:label="@string/app_name" >
   <intent-filter>
    <action android:name="android.intent.action.MAIN" />
 
    <category android:name="android.intent.category.LAUNCHER" />
   </intent-filter>
  </activity>
 </application>
 
</manifest>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 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="com.itheima28.memorydemo.MainActivity$PlaceholderFragment" >
 
 <TextView
  android:id="@+id/tv_memory_info"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_centerInParent="true"/>
 
</RelativeLayout>

package com.itheima28.memorydemo;
 
import Java.io.File;
 
import android.os.Bundle;
import android.os.Environment;
import android.os.StatFs;
import android.support.v7.app.ActionBarActivity;
import android.text.format.Formatter;
import android.widget.TextView;
 
public class MainActivity extends ActionBarActivity {
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  TextView tvMemoryInfo = (TextView) findViewById(R.id.tv_memory_info);
  
  //获得sd卡的内存状态
  File sdcardFileDir = Environment.getExternalStorageDirectory();
  String sdcardMemory = getMemoryInfo(sdcardFileDir);
 
  //获得手机内部存储控件的状态
  File dataFileDir = Environment.getDataDirectory();
  String dataMemory = getMemoryInfo(dataFileDir);
 
  tvMemoryInfo.setText("SD卡: " + sdcardMemory + "\n手机内部: " + dataMemory);
 }
 
 /**
  * 根据路径获取内存状态
  * @param path
  * @return
  */
 @SuppressWarnings("deprecation")
 private String getMemoryInfo(File path) {
  //获得一个磁盘状态对象
  StatFs stat = new StatFs(path.getPath());
  
  //获得一个扇区的大小
  long blockSize = stat.getBlockSize();
 
  //获得扇区的总数
  long totalBlocks = stat.getBlockCount();
  
  //获得可用的扇区数量
  long availableBlocks = stat.getAvailableBlocks();
 
  //总空间
  String totalMemory = Formatter.formatFileSize(this, totalBlocks * blockSize);
  
  //可用空间
  String availableMemory = Formatter.formatFileSize(this, availableBlocks * blockSize);
  
  return "总空间：" + totalMemory + "\n可用空间：" + availableMemory;
 }
}