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：

[java] view
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/**

* 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_S***E_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;

直接上代码：

[java] view
plaincopy





package com.android.clearmemory;



import android.app.Activity;

import android.app.ActivityManager;

import android.app.ActivityManager.MemoryInfo;

import android.app.ActivityManager.RunningAppProcessInfo;

import android.content.Context;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.Toast;



import java.util.List;



public class ClearMemoryActivity extends Activity {

private static final String TAG = "ClearMemoryActivity";



/**

* Called when the activity is first created.

*/

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);



Button clear = (Button) findViewById(R.id.clear);

clear.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(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(ClearMemoryActivity.this);

Log.d(TAG, "-----------before memory info : " + beforeMem);

int count = 0;

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

Log.d(TAG, "It will be killed, package name : " + pkgList[j]);

am.killBackgroundProcesses(pkgList[j]);

count++;

}

}



}

}



long afterMem = getAvailMemory(ClearMemoryActivity.this);

Log.d(TAG, "----------- after memory info : " + afterMem);

Toast.makeText(ClearMemoryActivity.this, "clear " + count + " process, "

+ (afterMem - beforeMem) + "M", Toast.LENGTH_LONG).show();

}

});



ClearMemoryFloatView.instance(getApplicationContext()).createView();

}



//获取可用内存大小

private long getAvailMemory(Context context) {

// 获取android当前可用内存大小

ActivityManager am = (ActivityManager) context.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。