活动泄漏是针对当前问题我能想到的最具体的术语。如果它变成了别的东西，请纠正我。
场景：我创建了一个简单的 Android 测试应用程序来解决我的问题。我有一个活动，一个添加到片段容器的片段，以及一个从源获取数据的单独线程（在测试应用程序中，它只是创建数据本身）并通过 LocalBroadcastManager 将其中继到活动，其中反过来，活动使用数据来更新正在显示的片段。注意：我在 Nexus 4 上使用 android-support-v7-appcompat、support-v4 片段、API18。
问题：当应用程序第一次启动时，一切都按原样运行（此时发送到 logcat 的“奇怪的东西”是正常的）。问题在轮换、配置更改后开始出现。旋转后，“奇怪的东西”应该仍然会自行弹出；但是，事实并非如此。旋转后，活动检测到一个空片段并设置我的调试标志；之后，“奇怪的东西”永远不会再次出现，只会出现“null frag”或“frag there”。因此，我的问题和困惑。注意：你做的旋转越多，你得到的每个“奇怪的”语句的“null frag”语句就越多。
这是重新创建问题所需的代码：
MainActivity.java：
package com.example.myfragthreadtest;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.content.LocalBroadcastManager;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;
public class MainActivity extends ActionBarActivity {
public static final String DEBUG_TAG = "MainActivity";
public static final String OUTPUT_FRAGMENT = "OUTPUT_FRAGMENT";
public static final String SAVED_DATA = "SAVED_DATA";
public static final String UPDATE_SENT = "UPDATE_SENT";
public static final String UPDATE_DATA = "UPDATE_DATA";
private int myData;
private MyFragment outputFrag;
private volatile boolean debugFragFlag = false;
private MyThread myThread;
// Create a BroadcastReceiver for updates
private final BroadcastReceiver uiUpdateReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// Check action
if(UPDATE_SENT.equals(action)) {
myData = intent.getIntExtra(UPDATE_DATA, -1);
if(myData == -1) {
Log.d(DEBUG_TAG, "uiUpdateReceiver: data == -1");
return;
}
updateUI(myData);
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myData = -2;
myThread = null;
// Register broadcast receivers
LocalBroadcastManager.getInstance(this)
.registerReceiver(uiUpdateReceiver,
new IntentFilter(UPDATE_SENT));
}
@Override
protected void onStart() {
super.onStart();
if(findViewById(R.id.fragment_container) != null) {
outputFrag = (MyFragment) getSupportFragmentManager()
.findFragmentByTag(OUTPUT_FRAGMENT);
if(outputFrag != null) {
Log.d(DEBUG_TAG, "onStart: frag is there");
return;
}
Log.d(DEBUG_TAG, "onStart: frag is not there");
// Create new fragment and transaction
outputFrag = new MyFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment
transaction.add(R.id.fragment_container, outputFrag, OUTPUT_FRAGMENT);
transaction.commit();
}
else {
Log.e(DEBUG_TAG, "onCreate: No fragment container");
}
return;
}
@Override
protected void onRestoreInstanceState (Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
myData = savedInstanceState.getInt(SAVED_DATA);
outputFrag = (MyFragment) getSupportFragmentManager().findFragmentByTag(OUTPUT_FRAGMENT);
if(outputFrag == null) {
Log.d(DEBUG_TAG, "updateUI: null frag");
debugFragFlag = true;
return;
}
outputFrag.updateOutput(myData);
}
@Override
protected void onResume() {
super.onResume();
myThread = new MyThread(this, myData);
myThread.start();
}
@Override
protected void onSaveInstanceState (Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(SAVED_DATA, myData);
return;
}
@Override
protected void onDestroy() {
super.onDestroy();
// close out the data thread
myThread.close();
return;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
private void updateUI(int data) {
runOnUiThread(new Runnable() {
public void run() {
// Update UI
outputFrag = (MyFragment) getSupportFragmentManager()
.findFragmentByTag(OUTPUT_FRAGMENT);
if(outputFrag == null) {
Log.d(DEBUG_TAG, "updateUI: null frag");
debugFragFlag = true;
return;
}
else if(debugFragFlag) {
Log.d(DEBUG_TAG, "updateUI: frag there");
}
else {
Log.i(DEBUG_TAG, "updateUI: something weird");
}
outputFrag.updateOutput(myData);
}
});
return;
}
}
MyFragment.java：
package com.example.myfragthreadtest;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ScrollView;
import android.widget.TextView;
public class MyFragment extends Fragment {
private static final String DEBUG_TAG = "MyFragment";
// UI components for updating
private TextView console;
private ScrollView consoleScroller;
public void updateOutput(int data) {
// Update UI
setConsoleText(data);
return;
}
private void setConsoleText(int data) {
// Check that we have the UI components we want to update
if(console == null || consoleScroller == null) {
Log.d(DEBUG_TAG, "setConsoleText: null views");
return;
}
// Update UI
console.setText("Data" + data);
console.invalidate();
consoleScroller.fullScroll(View.FOCUS_DOWN);
consoleScroller.invalidate();
return;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
console = null;
consoleScroller = null;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.frag_layout, container, false);
}
@Override
public void onActivityCreated (Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// Get UI components for updating
console = (TextView)getView().findViewById(R.id.output_console);
consoleScroller = (ScrollView)getView().findViewById(R.id.console_scroller);
}
@Override
public void onDestroy() {
super.onDestroy(); // Always call the superclass
console = null;
consoleScroller = null;
return;
}
}
MyThread.java：
package com.example.myfragthreadtest;
import android.content.Context;
import android.content.Intent;
import android.support.v4.content.LocalBroadcastManager;
import android.util.Log;
public class MyThread extends Thread {
private static final String DEBUG_TAG = "MyThread";
private Context appContext;
private volatile boolean run;
private int counter;
public MyThread(Context context) {
this.appContext = context.getApplicationContext();
this.run = false;
this.counter = 0;
}
public MyThread(Context context, int data) {
this.appContext = context.getApplicationContext();
this.run = false;
this.counter = data;
}
public void run() {
run = true;
// Keep adding 1 every second
while (run) {
// Send update to the UI activity
Intent intent = new Intent();
intent.setAction(MainActivity.UPDATE_SENT);
intent.putExtra(MainActivity.UPDATE_DATA, counter++);
LocalBroadcastManager.getInstance(appContext).sendBroadcastSync(intent);
try {
Thread.sleep(3000);
} catch(Exception e) {
Log.d(DEBUG_TAG, "run: Sleep Failed.");
}
}
return;
}
// Call this from the main activity to shutdown the connection
public void close() {
run = false;
return;
}
}
frag_layout.xml：
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/console_scroller"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<TextView
android:id="@+id/output_console"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/hello_world"
android:textSize="25sp" >
</TextView>
</LinearLayout>
</ScrollView>
活动主.xml：
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
这是我看到的 logcat 输出： 旋转之前：
10-17 09:47:24.885: D/MainActivity(23085): onStart: frag is not there
10-17 09:47:24.905: E/MainActivity(23085): updateUI: something weird
10-17 09:47:24.935: D/libEGL(23085): loaded /system/lib/egl/libEGL_adreno200.so
10-17 09:47:24.945: D/libEGL(23085): loaded /system/lib/egl/libGLESv1_CM_adreno200.so
10-17 09:47:24.945: D/libEGL(23085): loaded /system/lib/egl/libGLESv2_adreno200.so
10-17 09:47:24.945: I/Adreno200-EGL(23085): <qeglDrvAPI_eglInitialize:265>: EGL 1.4 QUALCOMM Build: Iabe52cfaeae4c5fab1acacfe6f056ba15fa93274
10-17 09:47:24.985: D/OpenGLRenderer(23085): Enabling debug mode 0
10-17 09:47:27.898: D/MainActivity(23085): uiUpdateReceiver: data == -1
10-17 09:47:30.891: E/MainActivity(23085): updateUI: something weird
10-17 09:47:33.894: E/MainActivity(23085): updateUI: something weird
10-17 09:47:36.897: E/MainActivity(23085): updateUI: something weird
旋转后：
10-17 09:47:37.018: D/MainActivity(23085): onStart: frag is there
10-17 09:47:37.038: D/MainActivity(23085): updateUI: null frag
10-17 09:47:37.038: E/MainActivity(23085): updateUI: something weird
10-17 09:47:40.011: D/MainActivity(23085): updateUI: null frag
10-17 09:47:40.011: E/MainActivity(23085): updateUI: something weird
10-17 09:47:43.014: D/MainActivity(23085): updateUI: null frag
10-17 09:47:43.014: E/MainActivity(23085): updateUI: something weird
10-17 09:47:46.017: D/MainActivity(23085): updateUI: null frag
10-17 09:47:46.017: E/MainActivity(23085): updateUI: something weird
尽管仅查看应用程序看起来一切都很好，但如果有人旋转太多，我认为这可能会导致问题。