java - 应用程序关闭后恢复 Android 返回堆栈

Question

管理/恢复应用程序的最佳实践是什么 back stack在多个 session 之间？

工作流程示例:

1. Activity A 开始(堆栈:A)
2. Activity B 开始(堆栈:A B)
3. Activity C 开始(堆栈:A B C)
4. ...
5. 用户使用不同的应用程序(假设是 GMail 应用程序)一段时间
6. ...
7. 用户返回到我的应用程序，但返回堆栈已被 Android 清除。

在第 7 步，我想让 Activity C 恢复，如果用户按下后退按钮 2 次，它将返回到 Activity B，然后是 Activity A。

[编辑] 添加细节。

在上面的第 7 步之后，Android 中默认发生的是这样的:

1. Activity A 启动(堆栈:空，并添加 C)

而且我希望用户感觉他仍在使用相同的 session :

1. Activity C 恢复(堆栈:A B C)
2. 用户按下后退按钮，Activity B 恢复(堆栈:A B)
3. 用户按下后退按钮，Activity A 恢复(堆栈:A)

在避免内存泄漏的同时解决这种情况的好方法是什么？

[第二次编辑]我一直在设计一个解决方法，使用通用类 UIController 处理所有 Activity ，并使用 LauncherActivity 将逻辑委托(delegate)给 UIController。

因为我只需要在 ActivityC 启动时重建返回堆栈，这个解决方案似乎工作正常:

public class UIController
{
    private boolean _launched = false;

    static private final UIController __instance = new UIController();
    static public UIController getInstance() { return __instance; }

    // Enforces the Singleton Pattern by preventing external access to constructor
    private UIController() { }

    public void onActivityCreated(Activity activity) {
        if (!_launched)
        {
            if ( shouldRebuildStack() )
            {
                // Rebuild Activity stack

                // Npte : actually Android will add ActivityA and ActivityB to the stack
                // but will *NOT* create them right away. Only ActivityC will be 
                // created and resumed.
                // Since they are in the back stack, the other activities will be 
                // created by Android once needed.
                startActivity(activity, ActivityA.class);
                startActivity(activity, ActivityB.class);
                startActivity(activity, ActivityC.class);
            } else {
                // Starts default activity
                startActivity(activity, ActivityA.class);
            }

            _launched = true;
        }
    }

    public void onActivityResumed(Activity activity) {
        memorizeCurrentActivity( activity.getClass().toString() );
    }

    private void memorizeCurrentActivity( String className ) {
        // write className to preferences, disk, etc.
    }

    private boolean shouldRebuildStack() {
        String previousActivity = " [load info from file, preferences, etc.] ";
        return (previousActivity != null && previousActivity.equals("my.package.ActivityC"));
    }

    private void startActivity(Activity caller, Class newActivityClass)
    {
        Intent intent = new Intent(caller, newActivityClass);
        intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
        caller.startActivity( intent );
    }
}

// This is the default activity in the AndroidManifest.xml
// This prevents ActivityA from starting right away if the UIController
// wants to rebuild the stack.
public class LauncherActivity() {
    protected void onCreate(Bundle data) {
        super.onCreate(data);
        UIController.getInstance().onActivityCreated(this);
        finish();
    }
}

public class ActivityA() {
    protected void onCreate(Bundle data) {
        super.onCreate(data);
        UIController.getInstance().onActivityCreated(this);
    }
    protected void onResume() {
        super.onResume();
        UIController.getInstance().onActivityResumed(this);
    }
}

public class ActivityB() {
    // onCreate() & onResume(), same as ActivityA
}

public class ActivityC() {
    // onCreate() & onResume(), same as ActivityA
}

public class LauncherActivity() {
    protected void onCreate(Bundle data) {
        super.onCreate(data);
        UIController.getInstance().onActivityCreated(this);
        finish();
    }
}

public class ActivityA() {
    protected void onCreate(Bundle data) {
        super.onCreate(data);
        UIController.getInstance().onActivityCreated(this);
    }
    protected void onResume() {
        super.onResume();
        UIController.getInstance().onActivityResumed(this);
    }
}

public class ActivityB() {
    // same as ActivityA
}

public class ActivityC() {
    // same as ActivityA
}

如果有人有更好的解决方案，请随时发布。

Answer 1

听起来您应该将其设置为 true 并让 Android 处理 Activity 堆栈的管理。

android:alwaysRetainTaskState

If this attribute is set to "true" in the root activity of a task, the default behavior just described does not happen. The task retains all activities in its stack even after a long period.