Question

我有一个问题。我有两个活动 - MainActivity和ActivityB

一个。第一个活动（MainActivity）有一个按钮，它启动ActivityB

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                Intent activityB = new Intent(MainActivity.this, activityB.class);
                startActivity(activityB);
            }
        });

湾第二个活动的文本字段很少

当我在ActivityB中单击后退按钮然后应用切换到MainActivity，但我没有完成（）ActivityB。

如何在MainActivity上编程按钮，该按钮将检查ActivityB是否已创建。如果是，只需切换到ActivityB（可能在文本字段中有一些类型化的数据），否则创建ActivityB并切换到它???

此时每次点击按钮都会创建新的活动（新的文本字段等等，因此用户在数据之前会松散蠕动）。

我试过

android:launchMode="singleInstance"

和标志FLAG_ACTIVITY_REORDER_TO_FRONT ...

Answer 1

ActivityA - ＆gt; ActivityB - ＆gt; ActivityA（重复使用）

启动ActivityA时，在ActivityB中

：

使用FLAG：

    /**
     * When an existing singleTask activity is launched, 
     * all other activities above it in the stack will be destroyed.
     * It's different when launchMode is "Standard". 
     * The task which contains flag will come to the foreground 
     * and keep the state the same as before.
     * When you press HOME and launch the activity again, 
     * ActivityManger calls an intent
     *     {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER]
     *      flag=FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_IF_NEEDED cmp=A}    
     */

 Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP;

设置额外内容或操作

并在ActivityA中覆盖：

  /**
 * This is called for activities that set launchMode to "singleTop" in
 * their package, or if a client used the {@link Intent#FLAG_ACTIVITY_SINGLE_TOP}
 * flag when calling {@link #startActivity}.  In either case, when the
 * activity is re-launched while at the top of the activity stack instead
 * of a new instance of the activity being started, onNewIntent() will be
 * called on the existing instance with the Intent that was used to
 * re-launch it.
 *
 * <p>An activity will always be paused before receiving a new intent, so
 * you can count on {@link #onResume} being called after this method.
 *
 * <p>Note that {@link #getIntent} still returns the original Intent.  You
 * can use {@link #setIntent} to update it to this new Intent.
 *
 * @param intent The new intent that was started for the activity.
 *
 * @see #getIntent
 * @see #setIntent
 * @see #onResume
 */
@Override
protected void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    setIntent(intent);
    /** when we are back check here intent action for example or extras  */
}

多数民众赞成不是我的意思。请再读一次：如何在MainActivity上编程按钮，该按钮将检查ActivityB是否已创建。如果是，只需切换到ActivityB（可能在文本字段中有一些类型的数据），否则创建ActivityB并切换到它？ - Juliusz Hajdacki

@ juliusz-hajdacki是的，这正是你想要的:)

带按钮的第一个活动
按钮侦听器以标志
检查onNewIntent方法是否被激活或onCreate是否在第二个活动中
将结果返回给第一个活动（通过附加活动开始活动）
- 请再次仔细阅读:)

Android - 打开已经创建的Activity

1 个答案: