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解除。这一切都很好,除了当对话框打开时屏幕方向发生变化(背景线程正在运行)。此时,应用程序要么崩溃,要么死锁,要么进入一个奇怪的阶段,在所有线程被杀死之前,应用程序根本无法工作。

我如何处理屏幕方向的变化优雅?

下面的示例代码大致匹配我的实际程序:

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();
        }
    };
}

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)

我已经尝试在onSaveInstanceState中取消进度对话框,但这只是防止了立即崩溃。背景线程仍在运行,UI处于部分绘制状态。需要在它重新开始工作之前杀死整个应用程序。


当前回答

我的解决方案是扩展ProgressDialog类来获得我自己的MyProgressDialog。

我重新定义了show()和dismiss()方法来在显示对话框之前锁定方向,并在对话框被解散时将其解锁。

因此,当显示对话框并且设备的方向发生变化时,屏幕的方向保持不变,直到调用dismiss(),然后屏幕方向根据传感器值/设备方向发生变化。

这是我的代码:

public class MyProgressDialog extends ProgressDialog {
    private Context mContext;

    public MyProgressDialog(Context context) {
        super(context);
        mContext = context;
    }

    public MyProgressDialog(Context context, int theme) {
        super(context, theme);
        mContext = context;
    }
    
    public void show() {
        if (mContext.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT)
            ((Activity) mContext).setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        else
            ((Activity) mContext).setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
        super.show();
    }
    
    public void dismiss() {
        super.dismiss();
        ((Activity) mContext).setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
    }
}

其他回答

我发现了一个更容易的解决方案来处理线程时,方向改变。你可以只保留一个静态引用到你的活动/片段,并在对ui进行操作之前验证它是否为空。我建议使用try catch:

 public class DashListFragment extends Fragment {
     private static DashListFragment ACTIVE_INSTANCE;

     @Override
     public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ACTIVE_INSTANCE = this;

        new Handler().postDelayed(new Runnable() {
            public void run() {
                try {
                        if (ACTIVE_INSTANCE != null) {
                            setAdapter(); // this method do something on ui or use context
                        }
                }
                catch (Exception e) {}


            }
        }, 1500l);

    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        ACTIVE_INSTANCE = null;
    }


}

我也遇到了同样的问题,我想出了一个不使用ProgressDialog的解决方案,我得到了更快的结果。

我所做的是创建一个布局,其中有一个ProgressBar。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ProgressBar
    android:id="@+id/progressImage"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    />
</RelativeLayout>

然后在onCreate方法中执行以下操作

public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.progress);
}

然后在线程中执行长任务,完成后使用Runnable将内容视图设置为您想要用于此活动的实际布局。

例如:

mHandler.post(new Runnable(){

public void run() {
        setContentView(R.layout.my_layout);
    } 
});

这就是我所做的,我发现它比显示ProgressDialog运行得更快,在我看来,它的侵入性更小,外观更好。

然而,如果你想要使用ProgressDialog,那么这个答案不适合你。

我尝试执行jfelectron的解决方案,因为它是“解决这些问题的坚如磐石的解决方案,符合‘Android方式’”,但我花了一些时间来查找并整合所有提到的元素。最终得到了这个略有不同的,我认为更优雅的解决方案,完整地贴在这里。

使用从活动中触发的IntentService在单独的线程上执行长时间运行的任务。该服务向更新对话框的活动发出sticky Broadcast intent。Activity使用showDialog(), onCreateDialog()和onPrepareDialog()来消除在应用程序对象或savedInstanceState包中传递持久化数据的需要。无论应用程序如何中断,这都应该工作。

活动类:

public class TesterActivity extends Activity {
private ProgressDialog mProgressDialog;
private static final int PROGRESS_DIALOG = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    Button b = (Button) this.findViewById(R.id.test_button);
    b.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            buttonClick();
        }
    });
}

private void buttonClick(){
    clearPriorBroadcast();
    showDialog(PROGRESS_DIALOG);
    Intent svc = new Intent(this, MyService.class);
    startService(svc);
}

protected Dialog onCreateDialog(int id) {
    switch(id) {
    case PROGRESS_DIALOG:
        mProgressDialog = new ProgressDialog(TesterActivity.this);
        mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        mProgressDialog.setMax(MyService.MAX_COUNTER);
        mProgressDialog.setMessage("Processing...");
        return mProgressDialog;
    default:
        return null;
    }
}

@Override
protected void onPrepareDialog(int id, Dialog dialog) {
    switch(id) {
    case PROGRESS_DIALOG:
        // setup a broadcast receiver to receive update events from the long running process
        IntentFilter filter = new IntentFilter();
        filter.addAction(MyService.BG_PROCESS_INTENT);
        registerReceiver(new MyBroadcastReceiver(), filter);
        break;
    }
}

public class MyBroadcastReceiver extends BroadcastReceiver{
    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.hasExtra(MyService.KEY_COUNTER)){
            int count = intent.getIntExtra(MyService.KEY_COUNTER, 0);
            mProgressDialog.setProgress(count);
            if (count >= MyService.MAX_COUNTER){
                dismissDialog(PROGRESS_DIALOG);
            }
        }
    }
}

/*
 * Sticky broadcasts persist and any prior broadcast will trigger in the 
 * broadcast receiver as soon as it is registered.
 * To clear any prior broadcast this code sends a blank broadcast to clear 
 * the last sticky broadcast.
 * This broadcast has no extras it will be ignored in the broadcast receiver 
 * setup in onPrepareDialog()
 */
private void clearPriorBroadcast(){
    Intent broadcastIntent = new Intent();
    broadcastIntent.setAction(MyService.BG_PROCESS_INTENT);
    sendStickyBroadcast(broadcastIntent);
}}

IntentService经济舱:

public class MyService extends IntentService {

public static final String BG_PROCESS_INTENT = "com.mindspiker.Tester.MyService.TEST";
public static final String KEY_COUNTER = "counter";
public static final int MAX_COUNTER = 100;

public MyService() {
  super("");
}

@Override
protected void onHandleIntent(Intent intent) {
    for (int i = 0; i <= MAX_COUNTER; i++) {
        Log.e("Service Example", " " + i);
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        Intent broadcastIntent = new Intent();
        broadcastIntent.setAction(BG_PROCESS_INTENT);
        broadcastIntent.putExtra(KEY_COUNTER, i);
        sendStickyBroadcast(broadcastIntent);
    }
}}

清单文件条目:

应用前部分:

uses-permission android:name="com.mindspiker.Tester.MyService.TEST"
uses-permission android:name="android.permission.BROADCAST_STICKY"

应用程序内部部分

service android:name=".MyService"

将长任务移动到单独的类中。将其实现为主题-观察者模式。每当创建活动时,注册并在关闭时注销任务类。任务类可以使用AsyncTask。

这是一个非常古老的问题,出于某种原因出现在侧栏上。

如果后台任务只需要在活动处于前台时存活,“新的”解决方案是在保留的片段中托管后台线程(或者,最好是AsyncTask),如本开发指南和大量q&a中所述。

如果活动因配置更改而被销毁,则保留的片段将继续存在,但当活动在后台或后台堆栈中被销毁时则不存在。因此,如果onPause()中的isChangingConfigurations()为false,后台任务仍然应该被中断。