雖然我遵循Android Developers網站上的教程，但無法將我的活動綁定到我的服務。無法綁定到服務
package com.dieselboris.motioncapture;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import com.dieselboris.motioncapture.LocalService.LocalBinder;
public class HelloMotionCaptureActivity extends Activity implements OnClickListener {
private TextView textBox;
LocalService mService;
boolean mBound = false;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textBox = (TextView) findViewById(R.id.textView1);
}
@Override
protected void onStart() {
super.onStart();
// Bind to LocalService NEVER RETURNS TRUE!!!!
Intent intent = new Intent(this, LocalService.class);
boolean isBound = bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
String text = Boolean.toString(isBound);
textBox.setText(text);
}
@Override
protected void onStop() {
super.onStop();
// Unbind from the service
if (mBound) {
unbindService(mConnection);
mBound = false;
}
}
//start the service when clicked
public void onClick(View v) {
if (v == startButton)
{
//NEVER IN HERE
if (mBound) {
int num = mService.getRandomNumber();
Toast.makeText(this, "incoming number: " + num, Toast.LENGTH_LONG).show();
}
Toast.makeText(this, "the service should run now", Toast.LENGTH_LONG).show();
}
}
/** Defines callbacks for service binding, passed to bindService() */
private ServiceConnection mConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName className,
IBinder service) {
// We've bound to LocalService, cast the IBinder and get LocalService instance
LocalBinder binder = (LocalBinder) service;
mService = binder.getService();
mBound = true;
if (mBound) {
// Call a method from the LocalService.
// However, if this call were something that might hang, then this request should
// occur in a separate thread to avoid slowing down the activity performance.
int num = mService.getRandomNumber();
String text = Integer.toString(num);
textBox.setText(text);
}
}
@Override
public void onServiceDisconnected(ComponentName arg0) {
mBound = false;
}
};
}
我嘗試連接到服務：
package com.dieselboris.motioncapture;
import java.util.Random;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
public class LocalService extends Service {
// Binder given to clients
private final IBinder mBinder = new LocalBinder();
// Random number generator
private final Random mGenerator = new Random();
/**
* 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) {
return mBinder;
}
/** method for clients */
public int getRandomNumber() {
return mGenerator.nextInt(100);
}
}
我從仿真器輸出如下：
ERROR/AndroidRuntime（10878）：致命異常：主要
ERROR/AndroidRuntime（10878）：java.lang.NullPointerException
ERROR/AndroidRuntime（10878）：at com.dieselboris.motioncapture.HelloMotionCaptur eActivity.onClick（HelloMotionCaptureActivity.java:66）
ERROR/AndroidRuntime（10878）：at android.view.View.performClick（View.java:2408）
ERROR/AndroidRuntime（10878）：at android.view.View $ PerformClick.run（View.java:8817）
ERROR/AndroidRuntime（10878）：在android.os.Handler.handleCallback（Handler.java:587）
ERROR/AndroidRuntime（10878）：在android.os.Handler。 dispatchMessage（Handler.java:92）
ERROR/AndroidRuntime（10878）：at android.os.Looper.loop（Looper.java:144）
ERROR/AndroidRuntime（10878）：at android.app.ActivityThread.main（ ActivityThread.java:4937）
錯誤/ AndroidRuntime（ 10878）：at java.lang.reflect.Method.invokeNative（Native Method）
ERROR/AndroidRuntime（10878）：at java.lang.reflect.Method.invoke（Method.java:521）
ERROR/AndroidRuntime（10878） ）：at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:868）
ERROR/AndroidRuntime（10878）：at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:626 ）
ERROR/AndroidRuntime（10878）：在dalvik.system.NativeStart.main（本機方法）
看來，我稱之爲從服務公衆方法之前，它的初始化或連接尚未建立。
我仔細地在開發者網站上跟蹤了這個例子，並且無法弄清楚我做錯了什麼。