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。
我是这样做的:
package com.palewar;
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
public class ThreadActivity extends Activity {
static ProgressDialog dialog;
private Thread downloadThread;
final static Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
dialog.dismiss();
}
};
protected void onDestroy() {
super.onDestroy();
if (dialog != null && dialog.isShowing()) {
dialog.dismiss();
dialog = null;
}
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downloadThread = (Thread) getLastNonConfigurationInstance();
if (downloadThread != null && downloadThread.isAlive()) {
dialog = ProgressDialog.show(ThreadActivity.this, "",
"Signing in...", false);
}
dialog = ProgressDialog.show(ThreadActivity.this, "",
"Signing in ...", false);
downloadThread = new MyThread();
downloadThread.start();
// processThread();
}
// Save the thread
@Override
public Object onRetainNonConfigurationInstance() {
return downloadThread;
}
static public class MyThread extends Thread {
@Override
public void run() {
try {
// Simulate a slow network
try {
new Thread().sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.sendEmptyMessage(0);
} finally {
}
}
}
}
你也可以试着让我知道它对你是否有效
我是这样做的:
package com.palewar;
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
public class ThreadActivity extends Activity {
static ProgressDialog dialog;
private Thread downloadThread;
final static Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
dialog.dismiss();
}
};
protected void onDestroy() {
super.onDestroy();
if (dialog != null && dialog.isShowing()) {
dialog.dismiss();
dialog = null;
}
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downloadThread = (Thread) getLastNonConfigurationInstance();
if (downloadThread != null && downloadThread.isAlive()) {
dialog = ProgressDialog.show(ThreadActivity.this, "",
"Signing in...", false);
}
dialog = ProgressDialog.show(ThreadActivity.this, "",
"Signing in ...", false);
downloadThread = new MyThread();
downloadThread.start();
// processThread();
}
// Save the thread
@Override
public Object onRetainNonConfigurationInstance() {
return downloadThread;
}
static public class MyThread extends Thread {
@Override
public void run() {
try {
// Simulate a slow network
try {
new Thread().sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.sendEmptyMessage(0);
} finally {
}
}
}
}
你也可以试着让我知道它对你是否有效
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。
