我在Android应用程序中监听网络活动。当事件通过网络传来时，我想更新一些驻留在应用程序中不同片段内的TextView。现在我有一个单一的屏幕应用程序，其中一次有一个片段在屏幕上。
如何在由FragmentStatePagerAdapter管理的ViewPager内的现有Fragment上调用方法？
我能够＆＃34;画＆＃34; UI正确，它按预期在屏幕上显示。这一切都有效。我正在做的艰难时刻是在后台线程向我的包含Activity发送消息时调用方法。该线程长时间运行并会频繁更新每个TextView（想想倒数计时器）。
{thread} - ＆gt; Actvity.handleMessage（） - ＆gt; {当前} Fragment.update（）;
我试图辨别＆＃34;当前＆＃34;，onscreen Fragment是什么，以便我可以调用它上面的方法来更新它的TextViews。我试图使用我读过的findFragmentByTag方法，但它总是返回一个null Fragment对象。
具体来说，我这样做：
private String getFragmentTag(int viewPagerId, int fragmentPosition){
return "android:switcher:" + viewPagerId + ":" + fragmentPosition;
}
//Take the data from the thread (network) and react to it.
@Override
public boolean handleMessage(Message msg) {
//tell the fragment to update itself
//Log.v(TAG, "Handler: " + msg.what);
int currentFragmentIndex = pager.getCurrentItem();
Log.v(TAG, "Current Fragment Index: " + Integer.toString(currentFragmentIndex));
String fTag = getFragmentTag(pager.getId(), currentFragmentIndex );
Log.v(TAG, "Current Fragment Tag: " + fTag);
////THIS IS WHERE I AM HAVING TROUBLE!////
Log.v(TAG, "fragment: " + getSupportFragmentManager().findFragmentByTag(fTag));
////THIS ALWAYS OUTPUTS:
////fragment: null
//now do the update
//currentFragment.update(sensorDataMap);
return true;
}
基于阅读吨，特别是这篇文章 - How to get existing fragments when using FragmentPagerAdapter
以下是相关代码......
MainActivity.java
public class MainActivity extends FragmentActivity implements Callback {
//receive messages from the other thread
private Handler handler = new Handler(this);
//the runnable listening to the network
private UDPListener udpl;
//we will parse the handler data into this map and store the values by int keys
private SparseArray<String> sensorDataMap = new SparseArray<String>();
//for logging and convenience
private static final String TAG = "BRRT";
//set up the fragment manager
private ViewPager pager;
private ScreenFragmenStatePagerAdapter fragmentManager;
private ScreenFragment currentFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//remove the titlebar
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
//keep the screen on while we are running
this.getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
//set up the pager to move through the fragments
pager = (ViewPager) findViewById(R.id.viewPager);
fragmentManager = new ScreenFragmenStatePagerAdapter(getSupportFragmentManager());
pager.setAdapter(fragmentManager);
//start up the thread
Log.v(TAG, "start thread");
startUDPListener(handler);
Log.v(TAG, "past start thread");
}
//start up the thread to listen to the network, pass in the handle to this thread for messages
private void startUDPListener(Handler handler){
//spawn the listener thread, pass in the context and the handler object
try{
udpl = new UDPListener(this.getApplicationContext(), handler, sensorDataMap);
//TODO remove this debug flag
//DEBUG
udpl.setDebug(true);
//DEBUG
//set up the threaded reading, event throwing
Thread reader = new Thread(udpl);
reader.start();
} catch(Exception e){
//TODO real logging
Log.v(TAG, "caught after trying to start thread");
Log.v(TAG, e.getMessage());
}
}
//fragile, as this depends on the current naming convention for these fragment IDs in support/v4.
private String getFragmentTag(int viewPagerId, int fragmentPosition){
return "android:switcher:" + viewPagerId + ":" + fragmentPosition;
}
//Take the data from the thread (network) and react to it. This will get back unparsed strings
//and have to parse them in this thread, with the UI
@Override
public boolean handleMessage(Message msg) {
//tell the fragment to update itself
//Log.v(TAG, "Handler: " + msg.what);
int currentFragmentIndex = pager.getCurrentItem();
Log.v(TAG, "Current Fragment Index: " + Integer.toString(currentFragmentIndex));
String fTag = getFragmentTag(pager.getId(), currentFragmentIndex );
Log.v(TAG, "Current Fragment Tag: " + fTag);
Log.v(TAG, "fragment: " + getSupportFragmentManager().findFragmentByTag(fTag));
//Log.v(TAG, "Current Fragment Null? " + (currentFragment == null));
//now do the update
//currentFragment.update(sensorDataMap);
return true;
}
@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 true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
ScreenFragmenStatePagerAdapter .java
public class ScreenFragmenStatePagerAdapter extends FragmentStatePagerAdapter {
//the set of screens we are interested in.
private ArrayList<ScreenConfig> screens = new ArrayList<ScreenConfig>(6);
//for logging and convenience
private static final String TAG = "CC";
//convenience variable to let us know what screen we are pointing at, logically
private ScreenConfig currentScreenConfig;
public ScreenFragmenStatePagerAdapter(FragmentManager fm) {
super(fm);
//set up the data.
setupScreenData();
}
@Override
public Fragment getItem(int pos) {
//Log.v(TAG, "fragment pos: " + pos);
//hopefully this will always work
currentScreenConfig = screens.get(pos);
ScreenFragment sf;
if (currentScreenConfig.eventCount() == 1){
sf = OneUpScreen.newInstance();
} else {
sf = FourUpScreen.newInstance();
}
sf.setConfig(currentScreenConfig);
return sf;
}
@Override
public int getCount() {
return screens.size();
}
//class that maps the various events to their descriptions in a screen by screen way
//do all the grunt work of mapping screens to events
private void setupScreenData(){
//TODO convert this stuff to JSON so we can pass them around in Bundles
//a 1up screen
ScreenConfig configGun = new ScreenConfig("Gun");
configGun.addEvent(204, "TimeToGun","Ttg", "TTG");
screens.add(configGun);
//the rest are 4up screens
ScreenConfig configBowman = new ScreenConfig("Bowman");
configBowman.addEvent(5, "ExTws","Tws", "TWS");
configBowman.addEvent(34, "ExLayTimeOnStrb", "LayTimeOnStrb", "Time Stb");
configBowman.addEvent(37, "ExLayTimeOnPort", "LayTimeOnPort", "Time Prt");
configBowman.addEvent(113, "ExNextMarkTwa", "NextMarkTwa", "TWA");
screens.add(configBowman);
ScreenConfig configPit = new ScreenConfig("Pit");
configPit.addEvent(88, "ExMarkTime","MarkTime", "Time Mark");
configPit.addEvent(113, "ExNextMarkTwa", "NextMarkTwa", "Next TWA");
configPit.addEvent(111, "ExNextMarkRng", "NextMarkRng", "Next Range");
configPit.addEvent(112, "ExNextMarkBrg", "NextMarkBrg", "Next Brg");
screens.add(configPit);
ScreenConfig configUpwindTrimmer = new ScreenConfig("Upwind Trimmer");
configUpwindTrimmer.addEvent(5, "ExTws","Tws", "TWS");
configUpwindTrimmer.addEvent(1, "ExBsp", "Bsp", "BSP");
configUpwindTrimmer.addEvent(54, "ExTargBspN", "TargBspN", "Tgt BSP");
configUpwindTrimmer.addEvent(4, "ExTwa", "Twa", "TWA");
screens.add(configUpwindTrimmer);
ScreenConfig configDownwindTrimmer = new ScreenConfig("Downwind Trimmer");
configDownwindTrimmer.addEvent(5, "ExTws","Tws", "TWS");
configDownwindTrimmer.addEvent(4, "ExTwa", "Twa", "TWA");
configDownwindTrimmer.addEvent(53, "ExTargTwaN", "TargTwaN", "Tgt BSP");
configDownwindTrimmer.addEvent(58, "ExPolarBspPercent", "PolarBspPercent", "P Bsp %");
screens.add(configDownwindTrimmer);
ScreenConfig configHelmsman = new ScreenConfig("Helmsman");
configHelmsman.addEvent(5, "ExTws","Tws", "TWS");
configHelmsman.addEvent(1, "ExBsp", "Bsp", "BSP");
configHelmsman.addEvent(6, "ExTwd", "Twd", "TWD");
configHelmsman.addEvent(4, "ExTwa", "Twa", "TWA");
screens.add(configHelmsman);
}
}
activty_main.xml
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/viewPager"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
答案 0 :(得分：0)
好吧，我放弃了正常的方式，转而使用绿色机器人基于EventBus的架构。
以下是相关的java文件，可以帮助您了解我最终在这个问题上的位置。我基本上转到在我的网络线程中发布到EventBus并直接在我的片段中接收这些事件。它极大地简化了我的代码。在代码上有很多优化（例如将Fragment和Activity生命周期处理程序拉入中心类或接口），但这是将来的。
这是MainActivity.java文件。现在所有它（基本上）都设置了viewpager并启动了网络线程。
public class MainActivity extends FragmentActivity {
//the runnable listening to the network
private UDPListener udpl;
//for logging and convenience
private static final String TAG = "BRRT";
//set up the fragment manager
private ViewPager pager;
private ScreenFragmenStatePagerAdapter fragmentManager;
//we will parse the handler data into this map and store the values by int keys
private SparseArray<String> sensorDataMap = new SparseArray<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//remove the titlebar
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
//keep the screen on while we are running
this.getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
//set up the pager to move through the fragments
pager = (ViewPager) findViewById(R.id.viewPager);
fragmentManager = new ScreenFragmenStatePagerAdapter(getSupportFragmentManager());
pager.setAdapter(fragmentManager);
}
@Override
public void onResume(){
//start up the thread
Log.v(TAG, "start thread");
startUDPListener();
Log.v(TAG, "past start thread");
super.onResume();
}
//start up the thread to listen to the network, pass in the handle to this thread for messages
private void startUDPListener(){
//spawn the listener thread, pass in the context and the handler object
try{
udpl = new UDPListener(this.getApplicationContext(), sensorDataMap);
//TODO remove this debug flag
//DEBUG
udpl.setDebug(true);
//DEBUG
//set up the threaded reading, event throwing
Thread reader = new Thread(udpl);
reader.start();
} catch(Exception e){
//TODO real logging
Log.v(TAG, "caught after trying to start thread");
Log.v(TAG, e.getMessage());
}
}
@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 true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
这是片段。它所做的只是配置其视图，并在EventBus上监听事件。
public class OneUpScreen extends ScreenFragment {
private Button name;
private TextView c00Title, c00Data;
//DEBUG
public String title;
//DEBUG
private int counter = 0;
//for logging and convenience
private static final String TAG = "BRRT";
@Override
public void onResume(){
EventBus.getDefault().register(this);
super.onResume();
}
@Override
public void onDestroy(){
EventBus.getDefault().unregister(this);
super.onDestroy();
}
//process the bus messaging
public void onEventMainThread(ExpeditionEvent event){ <-- READ IT FROM THE BUS
Log.v(TAG, "OneUp event received: " + event.getEventId() + " : " + event.getEventScreenValue());
c00Data.setText(""+counter);
counter++;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.one_up_screen_layout, container, false);
name = (Button) v.findViewById(R.id.lblTitle);
c00Title = (TextView) v.findViewById(R.id.c00Title);
c00Data = (TextView) v.findViewById(R.id.c00Data);
Bundle bundle = this.getArguments();
//initial set up of the text on the screen
//null check
name.setText((bundle.getString("name") == null) ? "error" : bundle.getString("name"));
c00Title.setText((bundle.getString("c00Title") == null) ? "error" : bundle.getString("c00Title"));
title = bundle.getString("c00Title");
return v;
}
public OneUpScreen(){
}
public static OneUpScreen newInstance() {
OneUpScreen frag = new OneUpScreen();
return frag;
}
//attach the config for this instance.
@Override
public void setConfig(ScreenConfig sc){
//set up the data to paint the screen for the first time
Bundle b = new Bundle();
//now we have to parse some stuff into a bundle and send the bundle to the fragment
b.putString("name", sc.getName());
b.putString("c00Title", sc.getEvents().get(0).getCleanName());
b.putInt("c00Data", sc.getEvents().get(0).getEventID());
//pass it along
this.setArguments(b);
}
}
这是我在网络监听器中调用的，这是Runnable的run方法...
//throw out an event for each item
EventBus.getDefault().post(new ExpEvent(key, value)); <-- PUT IT ON THE BUS
<强>的Ta-DA !!!
我希望这会帮助下一个在Android中遇到ViewPager，FragmentStatePagerAdapters，Fragments或线程问题的人。