Android 一键清理、内存清理功能实现

360桌面、金山清理大师等都提供了一键清理、一键加速等功能，其实就是杀一些后台进程来达到释放内存的目的。

基本思路就是列出所有运行的进程，查看其重要值（RunningAppProcessInfo.importance，值越大说明进程重要程度越低），可以设定一个阈值，如果该进程的重要值大于该阈值，就可以杀掉该进程。

进程的重要值有以下几个等级：

/**
       * Constant for {@link #importance}: this is a persistent process.
       * Only used when reporting to process observers.
       * @hide
       */
      public static final int IMPORTANCE_PERSISTENT = 50;  

      /**
       * Constant for {@link #importance}: this process is running the
       * foreground UI.
       */
      public static final int IMPORTANCE_FOREGROUND = 100;  

      /**
       * Constant for {@link #importance}: this process is running something
       * that is actively visible to the user, though not in the immediate
       * foreground.
       */
      public static final int IMPORTANCE_VISIBLE = 200;  

      /**
       * Constant for {@link #importance}: this process is running something
       * that is considered to be actively perceptible to the user. An
       * example would be an application performing background music playback.
       */
      public static final int IMPORTANCE_PERCEPTIBLE = 130;  

      /**
       * Constant for {@link #importance}: this process is running an
       * application that can not save its state, and thus can't be killed
       * while in the background.
       * @hide
       */
      public static final int IMPORTANCE_CANT_SAVE_STATE = 170;  

      /**
       * Constant for {@link #importance}: this process is contains services
       * that should remain running.
       */
      public static final int IMPORTANCE_SERVICE = 300;  

      /**
       * Constant for {@link #importance}: this process process contains
       * background code that is expendable.
       */
      public static final int IMPORTANCE_BACKGROUND = 400;  

      /**
       * Constant for {@link #importance}: this process is empty of any
       * actively running code.
       */
      public static final int IMPORTANCE_EMPTY = 500;

需要权限：

<uses-permission android:name="android.permission.KILL_BACKGROUND_PROCESSES"/> 

具体操作代码如下：

package com.example.demo; 

import java.util.List; 

import android.app.Activity;
import android.app.ActivityManager;
import android.app.ActivityManager.MemoryInfo;
import android.app.ActivityManager.RunningAppProcessInfo;
import android.content.Context;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast; 

public class CleanProcessActivity extends Activity { 

  private static final String TAG = "Clean"; 

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_clean_process);
  }
  public void clean(View v){
    //To change body of implemented methods use File | Settings | File Templates.
    ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
    List<RunningAppProcessInfo> infoList = am.getRunningAppProcesses();
    List<ActivityManager.RunningServiceInfo> serviceInfos = am.getRunningServices(100);  

    long beforeMem = getAvailMemory(this);
    Log.d(TAG, "-----------before memory info : " + beforeMem);
    int count = 0;
    PackageManager pm = getPackageManager(); 

    if (infoList != null) {
      for (int i = 0; i < infoList.size(); ++i) {
        RunningAppProcessInfo appProcessInfo = infoList.get(i);
        Log.d(TAG, "process name : " + appProcessInfo.processName);
        //importance 该进程的重要程度 分为几个级别，数值越低就越重要。
        Log.d(TAG, "importance : " + appProcessInfo.importance);  

        // 一般数值大于RunningAppProcessInfo.IMPORTANCE_SERVICE的进程都长时间没用或者空进程了
        // 一般数值大于RunningAppProcessInfo.IMPORTANCE_VISIBLE的进程都是非可见进程，也就是在后台运行着
        if (appProcessInfo.importance > RunningAppProcessInfo.IMPORTANCE_VISIBLE) {
          String[] pkgList = appProcessInfo.pkgList;
          for (int j = 0; j < pkgList.length; ++j) {//pkgList 得到该进程下运行的包名
            String appName = null;
            try {
              appName = (String) pm.getApplicationLabel(pm.getApplicationInfo(pkgList[j], 0));
            } catch (NameNotFoundException e) {
              // TODO Auto-generated catch block
              e.printStackTrace();
            }
            Log.d(TAG, "It will be killed, package name : " + pkgList[j]+" -- "+appName );
            am.killBackgroundProcesses(pkgList[j]);
            count++;
          }
        }  

      }
    }  

    long afterMem = getAvailMemory(this);
    Log.d(TAG, "----------- after memory info : " + afterMem);
    Toast.makeText(this, "clear " + count + " process, "
          + (afterMem - beforeMem) + "M", Toast.LENGTH_LONG).show();
  }
  private long getAvailMemory(CleanProcessActivity cleanProcessActivity) {
    // 获取android当前可用内存大小
    ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
    MemoryInfo mi = new MemoryInfo();
    am.getMemoryInfo(mi);
    //mi.availMem; 当前系统的可用内存
    //return Formatter.formatFileSize(context, mi.availMem);// 将获取的内存大小规格化
    Log.d(TAG, "可用内存---->>>" + mi.availMem / (1024 * 1024));
    return mi.availMem / (1024 * 1024);
  }
}

注意：

我这里选择阈值是IMPORTANCE_VISIBLE级别的，也就是非可见的后台进程和服务会被杀掉（一些系统进程肯定除外）。
清理的效果跟金山清理大师和360桌面的一键清理效果差不多。

如果不想杀的太凶，可以选择IMPORTANCE_SERVICE级别，杀掉那些长时间没用或者空进程了，这个级别的清理力度不够大，达不到金山清理大师的效果。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。