进度对话框和后台线程处于活动状态时如何处理屏幕方向变化? [英] How to handle screen orientation change when progress dialog and background thread active?

问题描述

我的程序在后台线程中执行一些网络活动.在开始之前，它会弹出一个进度对话框.该对话框在处理程序上被关闭.这一切都很好，除非在对话框启动时屏幕方向发生变化(并且后台线程正在运行).此时应用要么崩溃，要么死锁，或者进入一个奇怪的阶段，在所有线程都被杀死之前，应用根本无法运行.

My program does some network activity in a background thread. Before starting, it pops up a progress dialog. The dialog is dismissed on the handler. This all works fine, except when screen orientation changes while the dialog is up (and the background thread is going). At this point the app either crashes, or deadlocks, or gets into a weird stage where the app does not work at all until all the threads have been killed.

如何优雅地处理屏幕方向变化?

How can I handle the screen orientation change gracefully?

下面的示例代码与我的真实程序所做的大致相符:

The sample code below matches roughly what my real program does:

public class MyAct extends Activity implements Runnable {
    public ProgressDialog mProgress;

    // UI has a button that when pressed calls send

    public void send() {
         mProgress = ProgressDialog.show(this, "Please wait", 
                      "Please wait", 
                      true, true);
        Thread thread = new Thread(this);
        thread.start();
    }

    public void run() {
        Thread.sleep(10000);
        Message msg = new Message();
        mHandler.sendMessage(msg);
    }

    private final Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            mProgress.dismiss();
        }
    };
}

堆栈:

E/WindowManager(  244): Activity MyAct has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@433b7150 that was originally added here
E/WindowManager(  244): android.view.WindowLeaked: Activity MyAct has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@433b7150 that was originally added here
E/WindowManager(  244):     at android.view.ViewRoot.<init>(ViewRoot.java:178)
E/WindowManager(  244):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:147)
E/WindowManager(  244):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:90)
E/WindowManager(  244):     at android.view.Window$LocalWindowManager.addView(Window.java:393)
E/WindowManager(  244):     at android.app.Dialog.show(Dialog.java:212)
E/WindowManager(  244):     at android.app.ProgressDialog.show(ProgressDialog.java:103)
E/WindowManager(  244):     at android.app.ProgressDialog.show(ProgressDialog.java:91)
E/WindowManager(  244):     at MyAct.send(MyAct.java:294)
E/WindowManager(  244):     at MyAct$4.onClick(MyAct.java:174)
E/WindowManager(  244):     at android.view.View.performClick(View.java:2129)
E/WindowManager(  244):     at android.view.View.onTouchEvent(View.java:3543)
E/WindowManager(  244):     at android.widget.TextView.onTouchEvent(TextView.java:4664)
E/WindowManager(  244):     at android.view.View.dispatchTouchEvent(View.java:3198)

我试图关闭 onSaveInstanceState 中的进度对话框，但这只会防止立即崩溃.后台线程还在继续，UI处于部分绘制状态.需要在整个应用程序重新开始工作之前终止它.

I have tried to dismiss the progress dialog in onSaveInstanceState, but that just prevents an immediate crash. The background thread is still going, and the UI is in partially drawn state. Need to kill the whole app before it starts working again.

推荐答案

当你切换方向时，Android 会创建一个新的 View.您可能会崩溃，因为您的后台线程正在尝试更改旧线程的状态.(也可能有问题，因为你的后台线程不在 UI 线程上)

When you switch orientations, Android will create a new View. You're probably getting crashes because your background thread is trying to change the state on the old one. (It may also be having trouble because your background thread isn't on the UI thread)

我建议让 mHandler 可变并在方向改变时更新它.

I'd suggest making that mHandler volatile and updating it when the orientation changes.

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