Question

当您尝试startActivityForResult Activity launchMode="singleTask"时;它不会返回onActivityResult的任何值，并且当您设置launchMode="standard"时;一切正常，但系统要求说这Activity必须是singleTask，无论如何要解决这个问题？

Answer 1

startActivityForResult的文档说：

For example, if the activity you are launching uses the singleTask launch mode,
it will not run in your task and thus you will immediately receive a cancel result.

似乎没有办法解决这个问题。

如果您是名为Activity的开发人员，则可以在某些结果可用时发送广播。然后，呼叫活动可以列出到这个广播。

Answer 2

答案显示在班级startActivityUncheckedLocked的功能ActivityStackSupervisor中。在Android 5.x之前，当启动一个活动时，如果launchMode是singleTask或singleInstance，它将首先检查launchMode并将FLAG_ACTIVITY_NEW_TASK添加到launchFlags。如果活动的launchFlags包含FLAG_ACTIVITY_NEW_TASK，它将立即发回取消并让新任务继续正常启动，而不依赖于其创建者。

if (sourceRecord == null) {
    // This activity is not being started from another...  in this
    // case we -always- start a new task.
    if ((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) == 0) {
        Slog.w(TAG, "startActivity called from non-Activity context; forcing " +
                "Intent.FLAG_ACTIVITY_NEW_TASK for: " + intent);
        launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
    }
} else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
    // The original activity who is starting us is running as a single
    // instance...  this new activity it is starting must go on its
    // own task.
    launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
} else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
        || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
    // The activity being started is a single instance...  it always
    // gets launched into its own task.
    launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
}
// ......
if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
    // For whatever reason this activity is being launched into a new
    // task...  yet the caller has requested a result back.  Well, that
    // is pretty messed up, so instead immediately send back a cancel
    // and let the new task continue launched as normal without a
    // dependency on its originator.
    Slog.w(TAG, "Activity is launching as a new task, so cancelling activity result.");
    r.resultTo.task.stack.sendActivityResultLocked(-1,
            r.resultTo, r.resultWho, r.requestCode,
        Activity.RESULT_CANCELED, null);
    r.resultTo = null;
}

但是在Android 5.x中，这改变如下：

final boolean launchSingleTop = r.launchMode == ActivityInfo.LAUNCH_SINGLE_TOP;
final boolean launchSingleInstance = r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE;
final boolean launchSingleTask = r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK;
int launchFlags = intent.getFlags();
if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_DOCUMENT) != 0 &&
        (launchSingleInstance || launchSingleTask)) {
    // We have a conflict between the Intent and the Activity manifest, manifest wins.
    Slog.i(TAG, "Ignoring FLAG_ACTIVITY_NEW_DOCUMENT, launchMode is " +
            "\"singleInstance\" or \"singleTask\"");
    launchFlags &=
            ~(Intent.FLAG_ACTIVITY_NEW_DOCUMENT | Intent.FLAG_ACTIVITY_MULTIPLE_TASK);
} else {
    switch (r.info.documentLaunchMode) {
        case ActivityInfo.DOCUMENT_LAUNCH_NONE:
            break;
        case ActivityInfo.DOCUMENT_LAUNCH_INTO_EXISTING:
            launchFlags |= Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
            break;
        case ActivityInfo.DOCUMENT_LAUNCH_ALWAYS:
            launchFlags |= Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
            break;
        case ActivityInfo.DOCUMENT_LAUNCH_NEVER:
            launchFlags &= ~Intent.FLAG_ACTIVITY_MULTIPLE_TASK;
            break;
    }
}
final boolean launchTaskBehind = r.mLaunchTaskBehind
        && !launchSingleTask && !launchSingleInstance
        && (launchFlags & Intent.FLAG_ACTIVITY_NEW_DOCUMENT) != 0;
if (r.resultTo != null && (launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
    // For whatever reason this activity is being launched into a new
    // task...  yet the caller has requested a result back.  Well, that
    // is pretty messed up, so instead immediately send back a cancel
    // and let the new task continue launched as normal without a
    // dependency on its originator.
    Slog.w(TAG, "Activity is launching as a new task, so cancelling activity result.");
    r.resultTo.task.stack.sendActivityResultLocked(-1,
            r.resultTo, r.resultWho, r.requestCode,
            Activity.RESULT_CANCELED, null);
    r.resultTo = null;
}

即使您将launchMode设置为onActivityResult或singleTask，这也是{5.}}在Android 5.x中有效的原因。

Answer 3

@Peter Knego说什么

加

它似乎在5.1中工作，而不是在4.4.4

中

意味着onActivityResult会触发

Answer 4

要阐明一些答案：

API的
`startActivityForResult()`结合启动模式`singleTask`或`singleInstance`无效。 `onActivityResult()`将立即被调用，其结果代码为`Activity.RESULT_CANCELED`。

API的> = Android 5.x：

`startActivityForResult()`有效，但是启动模式`singleTask`或`singleInstance`基本上被忽略，这意味着该活动被启动到同一任务中，并且未创建新任务。< / p>
如果您要验证此运行`adb shell dumpsys activity activities`。我只希望系统至少会向我显示警告。

此更改也反映在@GGCoke具有posted的代码中。

Answer 5

我知道这已经很晚了，但你可以对onNewIntent（）方法产生OnActivityResult效果，因为这是你的singleTask活动。

onActivityResult使用launchMode =“singleTask”？

5 个答案:

API的> = Android 5.x：