android – ServiceConnection.onServiceConnected()在绑定到已启动的服务后从未调用过

概述在游戏应用程序中,我有以下场景： >从主游戏Activity中,玩家开始在后台运行的不同持续时间的几个游戏任务. >玩家应该能够在单独的视图中查看正在运行的游戏任务的进度. 为此,我创建了两个Activity和一个Service,定义如下： > Service ProgressService处理在并行线程上同时运行的多个ProgressBars. > Activity WorkScreen2创建一 在游戏应用程序中,我有以下场景：

>从主游戏Activity中,玩家开始在后台运行的不同持续时间的几个游戏任务.
>玩家应该能够在单独的视图中查看正在运行的游戏任务的进度.

为此,我创建了两个Activity和一个Service,定义如下：

> Service ProgressService处理在并行线程上同时运行的多个Progressbars.
> Activity WorkScreen2创建一个游戏任务,使用带有在Bundle中传递的任务参数的startService()启动服务.
> Activity ProgressScreen绑定到服务以获取并显示正在运行的任务的Progressbars.
>这两个活动都在一个tabactivity的单独TabHosts下运行.

我遇到的问题是从不调用ServiceConnection.onServiceConnected()方法.我得到一个Java.lang.NullPointerException,因为我尝试调用应该在此方法中分配的Service对象的方法.见下面的代码.

我使用getApplicationContext().bindService()将Activity绑定到服务,因为TabSpec cannot bind to Services.此方法返回true.因此,绑定是成功的.

这是服务：

public class ProgressService extends Service implements GameConstants {    public static final String broADCAST_PROGRESS = "com.mycompany.androID.mygame.progressbroadcast";    private static final long UPDATE_INTERVAL = 500;    private IBinder mBinder;    private List<Progressbar> mProgressbarList;    private List<String> mStaffnameList;    private final class ServiceHandler extends Handler {        public ServiceHandler(Looper looper) {            super(looper);        }        @OverrIDe        public voID handleMessage(Message msg) {            Progressbar progressbar = new Progressbar(ProgressService.this);            mProgressbarList.add(progressbar);            Bundle bundle = msg.getData();            String staffname = bundle.getString(WorkScreen2.STAFF_name);            mStaffnameList.add(staffname);            int taskDurationMillis = bundle.getInt(WorkScreen2.TASK_DURATION) * 1000;            progressbar.setMax(taskDurationMillis / 1000);            long startTimeMillis = SystemClock.uptimeMillis();            long elapsedtimeMillis = SystemClock.uptimeMillis()                    - startTimeMillis;            Intent intent = new Intent();            intent.setAction(broADCAST_PROGRESS);            while (elapsedtimeMillis < taskDurationMillis) {                try {                    Thread.sleep(UPDATE_INTERVAL);                } catch (InterruptedException e) {                    e.printstacktrace();                }                elapsedtimeMillis = SystemClock.uptimeMillis()                        - startTimeMillis;                int elapsedtimeSeconds = (int) elapsedtimeMillis / 1000;                progressbar.setProgress(elapsedtimeSeconds);                sendbroadcast(intent);            }            progressbar.setVisibility(VIEw.GONE);            mProgressbarList.remove(progressbar);            mStaffnameList.remove(staffname);            sendbroadcast(intent);            if (mProgressbarList.isEmpty()) {                stopSelf(msg.arg1);            }        }    }    @OverrIDe    public voID onCreate() {        super.onCreate();        mBinder = new ProgressServiceBinder();        mProgressbarList = Collections                .synchronizedList(new ArrayList<Progressbar>());        mStaffnameList = Collections.synchronizedList(new ArrayList<String>());    }    /*     * Creates a thread for each game task with parameters passed in     * <code>intent</code>     */    @OverrIDe    public int onStartCommand(Intent intent,int flags,int startID) {        Toast.makeText(this,"starting service",Toast.LENGTH_LONG).show();        HandlerThread thread = new HandlerThread("ServiceStartArguments",Process.THREAD_PRIORITY_BACKGROUND);        thread.start();        Handler serviceHandler = new ServiceHandler(thread.getLooper());        Message msg = serviceHandler.obtainMessage();        msg.arg1 = startID;        msg.setData(intent.getExtras());        serviceHandler.sendMessage(msg);        return START_STICKY;    }    @OverrIDe    public IBinder onBind(Intent intent) {        return mBinder;    }    public class ProgressServiceBinder extends Binder {        ProgressService getService() {            return ProgressService.this;        }    }    public List<Progressbar> getProgressbarList() {        return mProgressbarList;    }    public List<String> getStaffnameList() {        return mStaffnameList;    }    @OverrIDe    public voID onDestroy() {        Toast.makeText(this,"Service done",Toast.LENGTH_SHORT).show();    }}

这是绑定它的活动：

public class ProgressScreen extends ListActivity {    private final String TAG = "ProgressScreen";    private ProgressScreenAdapter mAdapter;    private ProgressService mProgressService;    private List<Progressbar> mProgressbarList;    private List<String> mStaffnameList;    @OverrIDe    public voID onCreate(Bundle bundle) {        Log.i(TAG,"ProgressScreen oncreate");        super.onCreate(bundle);        setContentVIEw(R.layout.progress_screen_layout);        IntentFilter filter = new IntentFilter();        filter.addAction(ProgressService.broADCAST_PROGRESS);        registerReceiver(receiver,filter);        dobindService();        mAdapter = new ProgressScreenAdapter(this,mStaffnameList,mProgressbarList);        setlistadapter(mAdapter); // Returns true        /*         * This is where I get the NullPointerException         * mProgressService is null here         */        mProgressbarList = mProgressService.getProgressbarList();        mStaffnameList = mProgressService.getStaffnameList();    }    @OverrIDe    protected voID onResume() {        super.onResume();        IntentFilter filter = new IntentFilter();        filter.addAction(ProgressService.broADCAST_PROGRESS);        registerReceiver(receiver,filter);    }    @OverrIDe    protected voID onPause() {        super.onPause();        unregisterReceiver(receiver);    }    boolean dobindService() {        return getApplicationContext().bindService(new Intent(this,ProgressService.class),mConnection,Context.BIND_auto_CREATE);    }    voID doUnbindService() {        getApplicationContext().unbindService(mConnection);    }    ServiceConnection mConnection = new ServiceConnection() {        public voID onServiceConnected(Componentname classname,IBinder binder) {            mProgressService = ((ProgressService.ProgressServiceBinder) binder).getService();            Toast.makeText(ProgressScreen.this,"Connected to ProgressService",Toast.LENGTH_SHORT).show();        }        public voID onServicedisconnected(Componentname name) {            mProgressService = null;        }    };    private broadcastReceiver receiver = new broadcastReceiver () {        @OverrIDe        public voID onReceive(Context context,Intent intent) {            mAdapter.notifyDataSetChanged();        }    };}

服务从主要活动开始如下：

Intent intent = new Intent(WorkScreen2.this,ProgressService.class);intent.putExtra(TASK_DURATION,task.getDuration());intent.putExtra(STAFF_name,staff.getname());startService(intent);

AndroIDManifest.xml包含

<service    androID:name=".ProgressService"    androID:label="@string/progress_service"></service>

解决方法 调用ServiceConnection的onServiceConnected(),但没有人保证在onCreate继续执行之前调用它.那么,这里发生了什么 – 你成功地绑定到服务(这就是为什么onBind返回true),但你还没有完全连接 – 尚未调用onServiceConnected(),因此你的本地mProgressService对象尚未初始化,因此你得到NullPointerException.

解：

移动这两行：

mProgressbarList = mProgressService.getProgressbarList();mStaffnameList = mProgressService.getStaffnameList();

从onCreate()到onServiceConnected()函数(在onServiceConnected()中初始化后使用服务对象).

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