Android创建前台运行的Service
Service如果要防止尽可能不被系统杀掉，需要设置为在前台运行。
由于设置前台运行service的方法在2.0之前和2.0之后有所变化。
所以需要根据不同的版本进行区分；或者完全使用反射机制来处理，这样只要有相应的方法就可以使用，否则使用其他版本的方法。
下面是一个设置servcie前台运行的例子，参考了API中对Service的说明。
http://developer.android.com/reference/android/app/Service.html#
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
import android.os.Build.VERSION;
import android.util.Log;
public class ForegroundService extends Service {
private static final String TAG = "ForegroundService";
private boolean mReflectFlg = false;
private static final int NOTIFICATION_ID = 1; // 如果id设置为0,会导致不能设置为前台service
private static final Class<?>[] mSetForegroundSignature = new Class[] {
boolean.class};
private static final Class<?>[] mStartForegroundSignature = new Class[] {
int.class, Notification.class};
private static final Class<?>[] mStopForegroundSignature = new Class[] {
boolean.class};
private NotificationManager mNM;
private Method mSetForeground;
private Method mStartForeground;
private Method mStopForeground;
private Object[] mSetForegroundArgs = new Object[1];
private Object[] mStartForegroundArgs = new Object[2];
private Object[] mStopForegroundArgs = new Object[1];
@Override
public void onCreate() {
super.onCreate();
Log.d(TAG, "onCreate");
mNM = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
try {
mStartForeground = ForegroundService.class.getMethod("startForeground", mStartForegroundSignature);
mStopForeground = ForegroundService.class.getMethod("stopForeground", mStopForegroundSignature);
} catch (NoSuchMethodException e) {
mStartForeground = mStopForeground = null;
}
try {
mSetForeground = getClass().getMethod("setForeground",
mSetForegroundSignature);
} catch (NoSuchMethodException e) {
throw new IllegalStateException(
"OS doesn't have Service.startForeground OR Service.setForeground!");
}
Notification.Builder builder = new Notification.Builder(this);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
new Intent(this, MainActivity.class), 0);
builder.setContentIntent(contentIntent);
builder.setSmallIcon(R.drawable.icon);
builder.setTicker("Foreground Service Start");
builder.setContentTitle("Foreground Service");
builder.setContentText("Make this service run in the foreground.");
Notification notification = builder.build();
startForegroundCompat(NOTIFICATION_ID, notification);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
super.onStartCommand(intent, flags, startId);
Log.d(TAG, "onStartCommand");
return START_STICKY;
}
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy");
stopForegroundCompat(NOTIFICATION_ID);
}
void invokeMethod(Method method, Object[] args) {
try {
method.invoke(this, args);
} catch (InvocationTargetException e) {
// Should not happen.
Log.w("ApiDemos", "Unable to invoke method", e);
} catch (IllegalAccessException e) {
// Should not happen.
Log.w("ApiDemos", "Unable to invoke method", e);
}
}
/**
* This is a wrapper around the new startForeground method, using the older
* APIs if it is not available.
*/
void startForegroundCompat(int id, Notification notification) {
if (mReflectFlg) {
// If we have the new startForeground API, then use it.
if (mStartForeground != null) {
mStartForegroundArgs[0] = Integer.valueOf(id);
mStartForegroundArgs[1] = notification;
invokeMethod(mStartForeground, mStartForegroundArgs);
return;
}
// Fall back on the old API.
mSetForegroundArgs[0] = Boolean.TRUE;
invokeMethod(mSetForeground, mSetForegroundArgs);
mNM.notify(id, notification);
} else {
/* 还可以使用以下方法，当sdk大于等于5时，调用sdk现有的方法startForeground设置前台运行，
* 否则调用反射取得的sdk level 5（对应Android 2.0）以下才有的旧方法setForeground设置前台运行 */
if(VERSION.SDK_INT >= 5) {
startForeground(id, notification);
} else {
// Fall back on the old API.
mSetForegroundArgs[0] = Boolean.TRUE;
invokeMethod(mSetForeground, mSetForegroundArgs);
mNM.notify(id, notification);
}
}
}
/**
* This is a wrapper around the new stopForeground method, using the older
* APIs if it is not available.
*/
void stopForegroundCompat(int id) {
if (mReflectFlg) {
// If we have the new stopForeground API, then use it.
if (mStopForeground != null) {
mStopForegroundArgs[0] = Boolean.TRUE;
invokeMethod(mStopForeground, mStopForegroundArgs);
return;
}
// Fall back on the old API. Note to cancel BEFORE changing the
// foreground state, since we could be killed at that point.
mNM.cancel(id);
mSetForegroundArgs[0] = Boolean.FALSE;
invokeMethod(mSetForeground, mSetForegroundArgs);
} else {
/* 还可以使用以下方法，当sdk大于等于5时，调用sdk现有的方法stopForeground停止前台运行，
* 否则调用反射取得的sdk level 5（对应Android 2.0）以下才有的旧方法setForeground停止前台运行 */
if(VERSION.SDK_INT >= 5) {
stopForeground(true);
} else {
// Fall back on the old API. Note to cancel BEFORE changing the
// foreground state, since we could be killed at that point.
mNM.cancel(id);
mSetForegroundArgs[0] = Boolean.FALSE;
invokeMethod(mSetForeground, mSetForegroundArgs);
}
}
}
}
前台Service运行后的效果如图：
（1）.通知栏显示内容：
（2）.下拉后通知栏显示内容：
