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。
If you're struggling with detecting orientation change events of a dialog INDEPENDENT OF AN ACTIVITY REFERENCE, this method works excitingly well. I use this because I have my own dialog class that can be shown in multiple different Activities so I don't always know which Activity it's being shown in. With this method you don't need to change the AndroidManifest, worry about Activity references, and you don't need a custom dialog (as I have). You do need, however, a custom content view so you can detect the orientation changes using that particular view. Here's my example:
设置
public class MyContentView extends View{
public MyContentView(Context context){
super(context);
}
@Override
public void onConfigurationChanged(Configuration newConfig){
super.onConfigurationChanged(newConfig);
//DO SOMETHING HERE!! :D
}
}
实现1 -对话
Dialog dialog = new Dialog(context);
//set up dialog
dialog.setContentView(new MyContentView(context));
dialog.show();
实现2 - AlertDialog。构建器
AlertDialog.Builder builder = new AlertDialog.Builder(context);
//set up dialog builder
builder.setView(new MyContentView(context)); //Can use this method
builder.setCustomTitle(new MycontentView(context)); // or this method
builder.build().show();
实现3 - ProgressDialog / AlertDialog
ProgressDialog progress = new ProgressDialog(context);
//set up progress dialog
progress.setView(new MyContentView(context)); //Can use this method
progress.setCustomTitle(new MyContentView(context)); // or this method
progress.show();
最初的问题是代码无法在屏幕方向改变时存活下来。显然,这是“解决”的程序处理屏幕方向变化本身,而不是让UI框架做它(通过调用onDestroy)。
I would submit that if the underlying problem is that the program will not survive onDestroy(), then the accepted solution is just a workaround that leaves the program with serious other problems and vulnerabilities. Remember that the Android framework specifically states that your activity is at risk for being destroyed almost at any time due to circumstances outside your control. Therefore, your activity must be able to survive onDestroy() and subsequent onCreate() for any reason, not just a screen orientation change.
如果你要接受自己处理屏幕方向变化来解决OP的问题,你需要验证onDestroy()的其他原因不会导致相同的错误。你能做到吗?如果不是,我会质疑这个“公认的”答案是否真的是一个很好的答案。
我也遇到过同样的情况。我所做的就是在整个应用程序中只获取一个进度对话框的实例。
首先,我创建了一个DialogSingleton类来只获得一个实例(Singleton模式)
public class DialogSingleton
{
private static Dialog dialog;
private static final Object mLock = new Object();
private static DialogSingleton instance;
private DialogSingleton()
{
}
public static DialogSingleton GetInstance()
{
synchronized (mLock)
{
if(instance == null)
{
instance = new DialogSingleton();
}
return instance;
}
}
public void DialogShow(Context context, String title)
{
if(!((Activity)context).isFinishing())
{
dialog = new ProgressDialog(context, 2);
dialog.setCanceledOnTouchOutside(false);
dialog.setTitle(title);
dialog.show();
}
}
public void DialogDismiss(Context context)
{
if(!((Activity)context).isFinishing() && dialog.isShowing())
{
dialog.dismiss();
}
}
}
正如我在这个类中所展示的,我将进度对话框作为属性。每次我需要显示一个进度对话框时,我都会获得唯一的实例并创建一个新的ProgressDialog。
DialogSingleton.GetInstance().DialogShow(this, "My title here!");
当我完成后台任务时,我再次调用惟一实例并关闭它的对话框。
DialogSingleton.GetInstance().DialogDismiss(this);
我将后台任务状态保存在共享首选项中。当我旋转屏幕时,我问我是否有这个活动的任务运行:(onCreate)
if(Boolean.parseBoolean(preference.GetValue(IS_TASK_NAME_EXECUTED_KEY, "boolean").toString()))
{
DialogSingleton.GetInstance().DialogShow(this, "Checking credentials!");
} // preference object gets the info from shared preferences (my own implementation to get and put data to shared preferences) and IS_TASK_NAME_EXECUTED_KEY is the key to save this flag (flag to know if this activity has a background task already running).
当我开始运行后台任务时:
preference.AddValue(IS_TASK_NAME_EXECUTED_KEY, true, "boolean");
DialogSingleton.GetInstance().DialogShow(this, "My title here!");
当我完成运行后台任务:
preference.AddValue(IS_TASK_NAME_EXECUTED_KEY, false, "boolean");
DialogSingleton.GetInstance().DialogDismiss(ActivityName.this);
我希望这能有所帮助。
我也遇到过同样的问题。我的活动需要从一个URL解析一些数据,它很慢。所以我创建了一个线程来完成这个任务,然后显示一个进度对话框。当线程完成时,我让线程通过处理程序发布消息回UI线程。在处理程序。handleMessage,我从线程获得数据对象(现在准备好了),并将其填充到UI。这和你的例子很相似。
经过反复试验,我似乎找到了解决办法。至少现在我可以在任何时候旋转屏幕,在线程完成之前或之后。在所有测试中,对话框都是正确关闭的,所有行为都符合预期。
我所做的如下所示。目标是填充我的数据模型(mDataObject),然后将其填充到UI。应该允许屏幕旋转在任何时候没有意外。
class MyActivity {
private MyDataObject mDataObject = null;
private static MyThread mParserThread = null; // static, or make it singleton
OnCreate() {
...
Object retained = this.getLastNonConfigurationInstance();
if(retained != null) {
// data is already completely obtained before config change
// by my previous self.
// no need to create thread or show dialog at all
mDataObject = (MyDataObject) retained;
populateUI();
} else if(mParserThread != null && mParserThread.isAlive()){
// note: mParserThread is a static member or singleton object.
// config changed during parsing in previous instance. swap handler
// then wait for it to finish.
mParserThread.setHandler(new MyHandler());
} else {
// no data and no thread. likely initial run
// create thread, show dialog
mParserThread = new MyThread(..., new MyHandler());
mParserThread.start();
showDialog(DIALOG_PROGRESS);
}
}
// http://android-developers.blogspot.com/2009/02/faster-screen-orientation-change.html
public Object onRetainNonConfigurationInstance() {
// my future self can get this without re-downloading
// if it's already ready.
return mDataObject;
}
// use Activity.showDialog instead of ProgressDialog.show
// so the dialog can be automatically managed across config change
@Override
protected Dialog onCreateDialog(int id) {
// show progress dialog here
}
// inner class of MyActivity
private class MyHandler extends Handler {
public void handleMessage(msg) {
mDataObject = mParserThread.getDataObject();
populateUI();
dismissDialog(DIALOG_PROGRESS);
}
}
}
class MyThread extends Thread {
Handler mHandler;
MyDataObject mDataObject;
// constructor with handler param
public MyHandler(..., Handler h) {
...
mHandler = h;
}
public void setHandler(Handler h) { mHandler = h; } // for handler swapping after config change
public MyDataObject getDataObject() { return mDataObject; } // return data object (completed) to caller
public void run() {
mDataObject = new MyDataObject();
// do the lengthy task to fill mDataObject with data
lengthyTask(mDataObject);
// done. notify activity
mHandler.sendEmptyMessage(0); // tell activity: i'm ready. come pick up the data.
}
}
这对我来说很有效。我不知道这是否是Android设计的“正确”方法——他们声称这种“在屏幕旋转期间破坏/重建活动”实际上使事情变得更简单,所以我猜这应该不是太棘手。
如果您在我的代码中发现问题,请告诉我。如上所述,我真的不知道是否有任何副作用。
编辑:谷歌工程师不推荐这种方法,正如Dianne Hackborn(又名hackbod)在StackOverflow的帖子中所描述的那样。查看这篇博客文章了解更多信息。
你必须把这个添加到manifest中的activity声明中:
android:configChanges="orientation|screenSize"
看起来是这样的
<activity android:label="@string/app_name"
android:configChanges="orientation|screenSize|keyboardHidden"
android:name=".your.package">
问题是,当配置发生更改时,系统将破坏活动。看到ConfigurationChanges。
所以把它放在配置文件中可以避免系统破坏你的活动。相反,它调用onConfigurationChanged(Configuration)方法。