Android判断应用程序从后台回到前台

MainActivity如下:

package cc.testbackgroundtofront;



import java.util.List;

import android.app.Activity;

import android.app.ActivityManager;

import android.app.ActivityManager.RunningTaskInfo;

import android.content.ComponentName;

import android.content.Context;

import android.content.SharedPreferences;

import android.content.SharedPreferences.Editor;

import android.os.Bundle;

import android.preference.PreferenceManager;

import android.widget.Toast;

/**

 * Demo描述:

 * 判断应用从后台回到前台

 * 即按下Home键后重新进入到应用

 */

public class MainActivity extends Activity {

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);

	}

	

	@Override

	protected void onResume() {

		super.onResume();

		

	}



	@Override

	protected void onRestart() {

		super.onRestart();

		SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());

		boolean isCurrentRunningForeground = prefs.getBoolean("isCurrentRunningForeground", false);

		if (!isCurrentRunningForeground) {

			Toast.makeText(MainActivity.this, "从后台回来", Toast.LENGTH_SHORT).show();

		}

	}

	@Override

	protected void onStop() {

		super.onStop();

		try {

			Thread.sleep(1000);

			new Thread(){

				public void run() {

					boolean isCurrentRunningForeground=isRunningForeground();

					SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());

					Editor editor=prefs.edit();  

					editor.putBoolean("isCurrentRunningForeground", isCurrentRunningForeground);

					editor.commit(); 

				};

			}.start();

		} catch (Exception e) {

			

		}

	}

	

	public boolean isRunningForeground(){

		String packageName=getPackageName(this);

		String topActivityClassName=getTopActivityName(this);

		System.out.println("packageName="+packageName+",topActivityClassName="+topActivityClassName);

		if (packageName!=null&&topActivityClassName!=null&&topActivityClassName.startsWith(packageName)) {

			System.out.println("---> isRunningForeGround");

			return true;

		} else {

			System.out.println("---> isRunningBackGround");

			return false;

		}

	}

	

	

	public  String getTopActivityName(Context context){

		String topActivityClassName=null;

		 ActivityManager activityManager =

		(ActivityManager)(context.getSystemService(android.content.Context.ACTIVITY_SERVICE )) ;

		 //android.app.ActivityManager.getRunningTasks(int maxNum) 

		 //int maxNum--->The maximum number of entries to return in the list

		 //即最多取得的运行中的任务信息(RunningTaskInfo)数量

	     List<RunningTaskInfo> runningTaskInfos = activityManager.getRunningTasks(1) ;

	     if(runningTaskInfos != null){

	    	 ComponentName f=runningTaskInfos.get(0).topActivity;

	    	 topActivityClassName=f.getClassName();

	    	

	     }

	     //按下Home键盘后 topActivityClassName=com.android.launcher2.Launcher

	     return topActivityClassName;

	}

	

	public String getPackageName(Context context){

		 String packageName = context.getPackageName();  

		 return packageName;

	}





}

 

main.xml如下:

<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"

    >



    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="判断应用是否是由后台回到前台"

        android:layout_centerInParent="true"

     />



</RelativeLayout>