您好，感谢您的帮助。
我有以下 Activity (请参阅下面的代码)。 Activity 绑定(bind)(或尝试绑定(bind))到服务。
该服务公开(或者应该公开)公共(public)方法 getNumber() 来检索号码。
当执行到
mService.getNumber()
应用程序停止返回 NullPointerException。
我进行了调试，我所能理解的是，由于某种原因，mService.getNumber() 导致了问题。
编辑:显然服务没有绑定(bind)，我在
之后测试了 mBound bool 值Intent intent = new Intent(this, LocalService.class);
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
它返回 false，因此服务没有绑定(bind)...问题就在那里!
感谢您的建议
public class Quotes extends Activity {
public LocalService mService;
boolean mBound = false;
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main);
// Bind to LocalService
Intent intent = new Intent(this, LocalService.class);
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
Log.e("", "arrivo a prima di loop");
for(int a=0;;a++){
SystemClock.sleep(500);
Log.e("", "sono nel loop");
int num =mService.getNumber();
Toast.makeText(this,Integer.toString(num), Toast.LENGTH_SHORT).show();
}
}
private ServiceConnection mConnection = new ServiceConnection() {
//@Override
public void onServiceConnected(ComponentName className,
IBinder service) {
Log.e("", "sono in ServiceConnection");
// We've bound to LocalService, cast the IBinder and get LocalService instance
LocalBinder binder = (LocalBinder) service;
mService = binder.getService();
mBound = true;
}
//@Override
public void onServiceDisconnected(ComponentName arg0) {
mBound = false;
}
};
这是服务的代码:
package com.example.quotes;
@TargetApi(3)
public class LocalService extends Service {
public int i;
// Binder given to clients
private final IBinder mBinder = new LocalBinder();
* Class used for the client Binder. Because we know this service always
* runs in the same process as its clients, we don't need to deal with IPC.
*/
public class LocalBinder extends Binder {
LocalService getService() {
// Return this instance of LocalService so clients can call public methods
return LocalService.this;
}
}
@Override
public IBinder onBind(Intent intent) {
Log.e("", "sono nel service");
new Task().execute();
return mBinder;
}
class Task extends AsyncTask<Void, String, Void> {
@Override
protected Void doInBackground(Void... unused) {
for (i=0;;i++) {
Log.e("Sono nel AsyncTask del Service", Integer.toBinaryString(i));
SystemClock.sleep(500);
}
//return(null);
}
}
public int getNumber() {
return i;
}
}
日志猫:
12-21 12:05:18.837: D/AndroidRuntime(889): Shutting down VM
12-21 12:05:18.837: W/dalvikvm(889): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
12-21 12:05:18.887: E/AndroidRuntime(889): FATAL EXCEPTION: main
12-21 12:05:18.887: E/AndroidRuntime(889): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.quotes/com.example.quotes.Quotes}: java.lang.NullPointerException
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.ActivityThread.access$600(ActivityThread.java:130)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.os.Handler.dispatchMessage(Handler.java:99)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.os.Looper.loop(Looper.java:137)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.ActivityThread.main(ActivityThread.java:4745)
12-21 12:05:18.887: E/AndroidRuntime(889): at java.lang.reflect.Method.invokeNative(Native Method)
12-21 12:05:18.887: E/AndroidRuntime(889): at java.lang.reflect.Method.invoke(Method.java:511)
12-21 12:05:18.887: E/AndroidRuntime(889): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-21 12:05:18.887: E/AndroidRuntime(889): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-21 12:05:18.887: E/AndroidRuntime(889): at dalvik.system.NativeStart.main(Native Method)
12-21 12:05:18.887: E/AndroidRuntime(889): Caused by: java.lang.NullPointerException
12-21 12:05:18.887: E/AndroidRuntime(889): at com.example.quotes.Quotes.onCreate(Quotes.java:91)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.Activity.performCreate(Activity.java:5008)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
12-21 12:05:18.887: E/AndroidRuntime(889): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
12-21 12:05:18.887: E/AndroidRuntime(889): ... 11 more
最佳答案
好的，找到了谜语的答案。
与服务的绑定(bind)是异步的。
只有调用onServiceConnected时，服务才被确定绑定(bind)；因此，在 onServiceConnected 中，我添加调用一个方法来启动需要在服务上执行的 Activity 。
再见
关于android - 绑定(bind)服务调用给出 NullPointerException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13990179/