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。
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"
如今,有一种更加独特的方式来处理这类问题。典型的方法是:
1. 确保你的数据与用户界面正确分离:
任何后台进程都应该在一个保留的Fragment中(使用Fragment. setretaininstance()设置此值)。这就成为了你的“持久数据存储”,你想要保留的任何数据都会被保留。在方向改变事件之后,这个片段仍然可以通过FragmentManager.findFragmentByTag()调用以其原始状态访问(当你创建它时,你应该给它一个标签而不是一个ID,因为它没有附加到一个视图)。
请参阅处理运行时更改开发指南,了解如何正确执行此操作,以及为什么这是最佳选择。
2. 确保你在后台进程和你的UI之间正确和安全的接口:
You must reverse your linking process. At the moment your background process attaches itself to a View - instead your View should be attaching itself to the background process. It makes more sense right? The View's action is dependent on the background process, whereas the background process is not dependent on the View.This means changing the link to a standard Listener interface. Say your process (whatever class it is - whether it is an AsyncTask, Runnable or whatever) defines a OnProcessFinishedListener, when the process is done it should call that listener if it exists.
这个答案很好地简洁地描述了如何定制侦听器。
3.每当UI被创建(包括方向的改变)时,将你的UI链接到数据过程中:
现在你必须考虑如何将后台任务与当前View结构连接起来。如果你正确地处理了你的方向变化(而不是人们经常推荐的configChanges黑客),那么你的对话框将被系统重新创建。这很重要,它意味着在方向改变时,所有Dialog的生命周期方法都会被召回。所以在这些方法中(onCreateDialog通常是一个好地方),你可以像下面这样调用:
DataFragment f = getActivity().getFragmentManager().findFragmentByTag("BACKGROUND_TAG");
if (f != null) {
f.mBackgroundProcess.setOnProcessFinishedListener(new OnProcessFinishedListener() {
public void onProcessFinished() {
dismiss();
}
});
}
查看Fragment生命周期以确定侦听器的设置最适合于您的个人实现。
这是一种通用方法,用于为本问题中问到的一般问题提供健壮而完整的解决方案。根据您的具体情况,这个答案中可能还缺少一些细节,但这通常是正确处理方向更改事件的最正确方法。
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。
这是我面对这个问题时的解决方案:
ProgressDialog不是一个Fragment子,所以我的自定义类“ProgressDialogFragment”可以扩展DialogFragment,以保持对话框显示的配置更改。
import androidx.annotation.NonNull;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.Bundle;
import androidx.fragment.app.DialogFragment;
import androidx.fragment.app.FragmentManager;
/**
* Usage:
* To display the dialog:
* >>> ProgressDialogFragment.showProgressDialogFragment(
* getSupportFragmentManager(),
* "fragment_tag",
* "my dialog title",
* "my dialog message");
*
* To hide the dialog
* >>> ProgressDialogFragment.hideProgressDialogFragment();
*/
public class ProgressDialogFragment extends DialogFragment {
private static String sTitle, sMessage;
private static ProgressDialogFragment sProgressDialogFragment;
public ProgressDialogFragment() {
}
private ProgressDialogFragment(String title, String message) {
sTitle = title;
sMessage = message;
}
@NonNull
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
return ProgressDialog.show(getActivity(), sTitle, sMessage);
}
public static void showProgressDialogFragment(FragmentManager fragmentManager, String fragmentTag, String title, String message) {
if (sProgressDialogFragment == null) {
sProgressDialogFragment = new ProgressDialogFragment(title, message);
sProgressDialogFragment.show(fragmentManager, fragmentTag);
} else { // case of config change (device rotation)
sProgressDialogFragment = (ProgressDialogFragment) fragmentManager.findFragmentByTag(fragmentTag); // sProgressDialogFragment will try to survive its state on configuration as much as it can, but when calling .dismiss() it returns NPE, so we have to reset it on each config change
sTitle = title;
sMessage = message;
}
}
public static void hideProgressDialogFragment() {
if (sProgressDialogFragment != null) {
sProgressDialogFragment.dismiss();
}
}
}
我们面临的挑战是在屏幕上保留对话框标题和消息
当它们重置为默认空字符串时旋转,尽管对话框仍然显示
有两种方法可以解决这个问题:
第一种方法:
使利用对话框的活动在manifest文件中的配置更改期间保留状态:
android:configChanges="orientation|screenSize|keyboardHidden"
谷歌不喜欢此方法。
第二种方法:
在活动的onCreate()方法上,如果savedInstanceState不为空,你需要通过重新构建ProgressDialogFragment来保留你的对话片段。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_deal);
if (savedInstanceState != null) {
ProgressDialogFragment saveProgressDialog = (ProgressDialogFragment) getSupportFragmentManager()
.findFragmentByTag("fragment_tag");
if (saveProgressDialog != null) {
showProgressDialogFragment(getSupportFragmentManager(), "fragment_tag", "my dialog title", "my dialog message");
}
}
}