基本介绍

通过ActivityManager获取到当前运行中的进程列表(getRunningAppProcesses)，每个进程的名字与对应应用ApplicationId相同。

如果当前运行进程列表中不存在与应用applicationId相同的进程，那么应用的进程肯定是处于被杀死的状态。

反之的话（即进程运行中），存在两种情况：

Activity任务栈不为空
Activity任务栈为空

如何判断任务栈？

通过activityManager.getRunningTasks(10)，获取到当前进程的任务栈列表。其中，列表中保存的是每个任务栈的对象ActivityManager.RunningTaskInfo。

其中getRunningTask(int maxNum)的入参，表示返回List的最大长度，一般会有两个任务栈（一为当前应用的任务栈，一为桌面启动的任务栈）

ActivityManager.RunningTaskInfo ：

numActivities 当前栈中Activity数量
baseActivity 栈底的Activity
topActivity 栈顶的Activity

具体代码

/**
 * 判断应用是否处于启动状态
 *
 * @param ctx         Content
 * @param packageName 要判断应用的 ApplicationId
 * @return Boolean true：进程活着并且应用的任务栈不为空； false：进程死亡或者应用的任务栈为空
 */
public static boolean isAppAlive(Context ctx, String packageName) {
    ActivityManager activityManager = (ActivityManager) ctx.getSystemService(Context.ACTIVITY_SERVICE);
    List<RunningAppProcessInfo> processInfos = activityManager.getRunningAppProcesses();

    for (int i = 0; i < processInfos.size(); i++) {
        RunningAppProcessInfo processInfo = processInfos.get(i);
        Logs.d(TAG, "isAppAlive: i = " + i + ", processName = " + processInfo.processName);
        if (processInfos.get(i).processName.equals(packageName)) {
            List<ActivityManager.RunningTaskInfo> runningTasks = activityManager.getRunningTasks(10);
            for (int j = 0; j < runningTasks.size(); j++) {
                ActivityManager.RunningTaskInfo taskInfo = runningTasks.get(j);
                Logs.i(TAG, "isAppAlive: i = " + j + ", taskInfo.baseActivity = " + taskInfo.baseActivity.getClassName() + ", taskInfo.topActivity = " + taskInfo.topActivity.getClassName());
                Logs.i(TAG, "isAppAlive: i = " + j + ", taskInfo.numActivities = " + taskInfo.numActivities + ", taskInfo.numRunning = " + taskInfo.numRunning +
                        ", taskInfo.description = " + taskInfo.description + ", taskInfo.describeContents() = " + taskInfo.describeContents());
                //在此处判断全限定类名时，应以包名为基准（当applicationId与packageName不一致时）
                if (taskInfo.baseActivity.getClassName().startsWith(packageName) && taskInfo.numActivities > 0) {
                    Logs.i(TAG, "isAppAlive: " + String.format(Locale.CHINA, "the %s is running, isAppAlive return true.", packageName));
                    return true;
                }
            }
        }
    }
    Logs.i(TAG, "isAppAlive: " + String.format(Locale.CHINA, "the %s is not running, isAppAlive return false.", packageName));
    return false;
}

场景日志

当前应用处于前台运行中，应用的任务栈处于第一位

isAppAlive: i = 0, taskInfo.baseActivity = com.jiedai.loan.ui.activity.HomeActivity, taskInfo.topActivity = com.jiedai.loan.ui.activity.LoginPasswordActivi
isAppAlive: i = 0, taskInfo.numActivities = 3, taskInfo.numRunning = 3, taskInfo.description = null, taskInfo.describeContents() = 0
isAppAlive: i = 1, taskInfo.baseActivity = com.meizu.flyme.launcher.Launcher, taskInfo.topActivity = com.meizu.flyme.launcher.Launcher
isAppAlive: i = 1, taskInfo.numActivities = 1, taskInfo.numRunning = 1, taskInfo.description = null, taskInfo.describeContents() = 0
isAppAlive: i = 0, processName = com.jiedai.loan
isAppAlive: i = 1, processName = com.jiedai.loan:pushcore

应用处于后台运行中（Home桌面状态），桌面启动任务栈处于第一位

isAppAlive: i = 0, taskInfo.baseActivity = com.meizu.flyme.launcher.Launcher, taskInfo.topActivity = com.meizu.flyme.launcher.Launcher
isAppAlive: i = 0, taskInfo.numActivities = 1, taskInfo.numRunning = 1, taskInfo.description = null, taskInfo.describeContents() = 0
isAppAlive: i = 1, taskInfo.baseActivity = com.jiedai.loan.ui.activity.HomeActivity, taskInfo.topActivity = com.jiedai.loan.ui.activity.LoginPasswordActivity
isAppAlive: i = 1, taskInfo.numActivities = 3, taskInfo.numRunning = 3, taskInfo.description = null, taskInfo.describeContents() = 0
isAppAlive: i = 0, processName = com.jiedai.loan
isAppAlive: i = 1, processName = com.jiedai.loan:pushcore

应用的任务栈仅有一个Activity时，栈底与栈顶是同一个Activity。

isAppAlive: i = 0, taskInfo.baseActivity = com.jiedai.loan.ui.activity.HomeActivity, taskInfo.topActivity = com.jiedai.loan.ui.activity.HomeActivity
isAppAlive: i = 0, taskInfo.numActivities = 1, taskInfo.numRunning = 1, taskInfo.description = null, taskInfo.describeContents() = 0
isAppAlive: i = 1, taskInfo.baseActivity = com.meizu.flyme.launcher.Launcher, taskInfo.topActivity = com.meizu.flyme.launcher.Launcher
isAppAlive: i = 1, taskInfo.numActivities = 1, taskInfo.numRunning = 1, taskInfo.description = null, taskInfo.describeContents() = 0
isAppAlive: i = 0, processName = com.jiedai.loan
isAppAlive: i = 1, processName = com.jiedai.loan:pushcore

应用进程活着，但是任务栈为空时，仅有一个桌面启动的任务栈

isAppAlive: i = 0, taskInfo.baseActivity = com.meizu.flyme.launcher.Launcher, taskInfo.topActivity = com.meizu.flyme.launcher.Launcher
isAppAlive: i = 0, taskInfo.numActivities = 1, taskInfo.numRunning = 1, taskInfo.description = null, taskInfo.describeContents() = 0
isAppAlive: i = 0, processName = com.jiedai.loan
isAppAlive: i = 1, processName = com.jiedai.loan:pushcore