【发布时间】：2015-05-11 11:16:59
【问题描述】：
我有一个在后台运行的服务，并且时不时地接收消息。 我希望应用能够连接到我的服务并接收这些消息。 所以我所做的是使用 AIDL 实现 IPC。我创建了两个 AIDL 文件： “IExtMessage”：
package com.tfl.extprotocolservice;
import com.tfl.extprotocolservice.ICallBackMessage;
interface IExtMessage{
void getMessage(ICallBackMessage cb);
}
和“ICallBackMessage”：
package com.tfl.extprotocolservice;
interface ICallBackMessage{
void onMessageReceived(int parameter,int state);
}
并创建了一个应用程序来接收这些消息来测试这个 IPC：
public class MainActivity extends Activity implements ServiceConnection{
private IExtMessage binding=null;
private parseParametersTask task=null;
HashMap<Integer,List<String>> parameters;
ParameterAlert alert;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
connectToService();
task=new parseParametersTask();
task.execute();
parameters=ReadParams.params;
}
public void connectToService(){
Intent implicit=new Intent(IExtMessage.class.getName());
List<ResolveInfo> matches=getPackageManager().queryIntentServices(implicit, 0);
if(matches.size()==0){
Toast.makeText(getApplicationContext(), "Cannot find a matching service!", Toast.LENGTH_LONG).show();
}
else if (matches.size()>1){
Toast.makeText(getApplicationContext(), "Found multiple matching services!", Toast.LENGTH_LONG).show();
}
else{
Toast.makeText(getApplicationContext(), "Found the Protocol Service", Toast.LENGTH_LONG).show();
Intent explicit=new Intent(implicit);
ServiceInfo svcInfo=matches.get(0).serviceInfo;
ComponentName cn=new ComponentName(svcInfo.applicationInfo.packageName, svcInfo.name);
explicit.setComponent(cn);
bindService(explicit, this, Context.BIND_AUTO_CREATE);
}
}
public void buttonClick(View v) {
if (v.getId() == R.id.navigation) {
DialogFragment dialog = new navigationChooserFragment();
dialog.show(getFragmentManager(), "navigation");
}
if(v.getId()==R.id.ptt){
PackageManager pm=getPackageManager();
Intent i=pm.getLaunchIntentForPackage("com.loudtalks");
i.addCategory(Intent.CATEGORY_LAUNCHER);
startActivity(i);
}
}
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Log.d("SERVICE", "Service Connected");
binding=IExtMessage.Stub.asInterface(service);
try {
binding.getMessage(cb);
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
Log.d("SERVICE","Service disconnected :(");
binding=null;
}
ICallBackMessage.Stub cb=new ICallBackMessage.Stub() {
@Override
public void onMessageReceived(int parameter,int state) throws RemoteException {
Log.d("SERVICE","received parameter "+parameter);
Log.d("SERVICE", "received state " + state);
FragmentManager fm=getFragmentManager();
FragmentTransaction ft=fm.beginTransaction();
if(state==1){
alert=new ParameterAlert();
Bundle bundleParam=new Bundle();
bundleParam.putInt("parameter",parameter);
alert.setArguments(bundleParam);
alert.show(ft,"alert");
}else {
if (alert.isVisible()) {
alert.dismiss();
}
}
}
};
class parseParametersTask extends AsyncTask<Void,Void,Void>{
@Override
protected Void doInBackground(Void... params) {
ReadParams readParams =new ReadParams();
try {
readParams.setInputFile(getAssets().open("parameters.xls"));
readParams.read();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
}
这是我服务中的相关代码：
public IBinder onBind(Intent intent) {
return (new ExtMessageBinder());
}
private static class ExtMessageBinder extends IExtMessage.Stub {
@Override
public void getMessage(ICallBackMessage cb) throws RemoteException {
L.m("TESTSERVICE","getMessage in Service called");
cb1 = cb;
}
}
cb1 是我在收到消息时保存的静态 ICallBackMessage 变量。 在我的服务中，这是传递消息的侦听器：
try {
cb1.onMessageReceived(carParameter, state);
} catch (RemoteException e1) {
// TODO Auto-generated catch block
L.m("TESTSERVICE", "" + e1);
}
所以，问题是，有时一切都很好，但有时我的服务会因为这个异常而崩溃：
05-11 13:55:28.763: E/AndroidRuntime(1924): FATAL EXCEPTION: main
05-11 13:55:28.763: E/AndroidRuntime(1924): java.lang.NullPointerException
05-11 13:55:28.763: E/AndroidRuntime(1924): at android.os.Parcel.readException(Parcel.java:1333)
05-11 13:55:28.763: E/AndroidRuntime(1924): at android.os.Parcel.readException(Parcel.java:1281)
05-11 13:55:28.763: E/AndroidRuntime(1924): at com.tfl.extprotocolservice.ICallBackMessage$Stub$Proxy.onMessageReceived(ICallBackMessage.java:83)
05-11 13:55:28.763: E/AndroidRuntime(1924): at com.tfl.extprotocolservice.ExtProtocolService$1.handleMessage(ExtProtocolService.java:127)
05-11 13:55:28.763: E/AndroidRuntime(1924): at android.os.Handler.dispatchMessage(Handler.java:99)
05-11 13:55:28.763: E/AndroidRuntime(1924): at android.os.Looper.loop(Looper.java:137)
05-11 13:55:28.763: E/AndroidRuntime(1924): at android.app.ActivityThread.main(ActivityThread.java:4424)
05-11 13:55:28.763: E/AndroidRuntime(1924): at java.lang.reflect.Method.invokeNative(Native Method)
05-11 13:55:28.763: E/AndroidRuntime(1924): at java.lang.reflect.Method.invoke(Method.java:511)
05-11 13:55:28.763: E/AndroidRuntime(1924): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-11 13:55:28.763: E/AndroidRuntime(1924): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-11 13:55:28.763: E/AndroidRuntime(1924): at dalvik.system.NativeStart.main(Native Method)
我不知道为什么会这样，也许我在某处或某处有泄漏。 我到处寻找，但找不到答案。
【问题讨论】：
-
你在用 cb1 做什么？
-
@pskink 我将它保存到一个静态变量中。当收到消息时，我对该变量有一个监听器。我编辑了我的问题并添加了代码来解释更多
-
有同样的问题。来自远程服务的回调。一个回调有效（它有一个自定义对象），另一个抛出异常（它也有一个自定义对象）。堆栈跟踪无法跟踪，错误在同一个地方（相同的两个 parcelReadExceptions()），我不知道如何调试它。