Android应用前后台的切换

• 判断APP是否在前台运行
• 将APP切换到前台

1. 判断APP是否在前台运行

 public static boolean isRunningForeground(Context context) {
        ActivityManager activityManager = (ActivityManager)context.getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> appProcessInfos = activityManager.getRunningAppProcesses();
        // 枚举进程
        for (ActivityManager.RunningAppProcessInfo appProcessInfo : appProcessInfos) {
            if (appProcessInfo.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                if (appProcessInfo.processName.equals(context.getApplicationInfo().processName)) {
                    return true;
                }
            }
        }
        return false;
    }

2. 将APP切换到前台

//如果APP是在后台运行
            if (!AllUtils.isRunningForeground(this)) {
                //获取ActivityManager
                ActivityManager mAm = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
                //获得当前运行的task
                List<ActivityManager.RunningTaskInfo> taskList = mAm.getRunningTasks(100);
                for (ActivityManager.RunningTaskInfo rti : taskList) {
                    //找到当前应用的task，并启动task的栈顶activity，达到程序切换到前台
                    if (rti.topActivity.getPackageName().equals(getPackageName())) {
                        mAm.moveTaskToFront(rti.id, 0);
                        return;
                    }
                }
                //若没有找到运行的task，用户结束了task或被系统释放，则重新启动mainactivity
                Intent resultIntent = new Intent(MainActivity.this, MainActivity.class);
                resultIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_SINGLE_TOP);
                startActivity(resultIntent);
            }

3. 必须添加的权限

<!--前后台的切换-->
    <uses-permission android:name="android.permission.GET_TASKS"/>
    <uses-permission android:name="android.permission.INTERACT_ACROSS_USERS_FULL"/>
    <uses-permission android:name="android.permission.GET_TOP_ACTIVITY_INFO"/>
    <uses-permission android:name="android.permission.REORDER_TASKS"/>

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