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 {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);}@Overrideprotected void onResume() {super.onResume();}@Overrideprotected 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();}}@Overrideprotected 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>

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