android 例子appdemos中一个本地service的例子。这里的activity优先级就高，但无论多高的优先级都不能保证不被销毁，除非是linux内核的东西。 看例子吧，不知道是不是有你想要的，看bingding那个内部类的东西就行了/* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.example.android.apis.app;import android.app.Notification; import android.app.NotificationManager; import android.app.PendingIntent; import android.app.Service; import android.content.Intent; import android.os.Binder; import android.os.IBinder; import android.util.Log; import android.widget.Toast;// Need the following import to get access to the app resources, since this // class is in a sub-package. import com.example.android.apis.R;/** * This is an example of implementing an application service that runs locally * in the same process as the application. The {@link LocalServiceActivities.Controller} * and {@link LocalServiceActivities.Binding} classes show how to interact with the * service. * * <p>Notice the use of the {@link NotificationManager} when interesting things * happen in the service. This is generally how background services should * interact with the user, rather than doing something more disruptive such as * calling startActivity(). */public class LocalService extends Service { private NotificationManager mNM; /** * Class for clients to access. 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 LocalService.this; } }
@Override public void onCreate() { mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE); // Display a notification about us starting. We put an icon in the status bar. showNotification(); } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.i("LocalService", "Received start id " + startId + ": " + intent); // We want this service to continue running until it is explicitly // stopped, so return sticky. return START_STICKY; } @Override public void onDestroy() { // Cancel the persistent notification. mNM.cancel(R.string.local_service_started); // Tell the user we stopped. Toast.makeText(this, R.string.local_service_stopped, Toast.LENGTH_SHORT).show(); } @Override public IBinder onBind(Intent intent) { return mBinder; } // This is the object that receives interactions from clients. See // RemoteService for a more complete example. private final IBinder mBinder = new LocalBinder(); /** * Show a notification while this service is running. */ private void showNotification() { // In this sample, we'll use the same text for the ticker and the expanded notification CharSequence text = getText(R.string.local_service_started); // Set the icon, scrolling text and timestamp Notification notification = new Notification(R.drawable.stat_sample, text, System.currentTimeMillis()); // The PendingIntent to launch our activity if the user selects this notification PendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, LocalServiceActivities.Controller.class), 0); // Set the info for the views that show in the notification panel. notification.setLatestEventInfo(this, getText(R.string.local_service_label), text, contentIntent); // Send the notification. // We use a layout id because it is a unique number. We use it later to cancel. mNM.notify(R.string.local_service_started, notification); } }
/* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.example.android.apis.app;import com.example.android.apis.R;import android.app.Activity; 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.Toast;public class LocalServiceActivities { /** * <p>Example of explicitly starting and stopping the local service. * This demonstrates the implementation of a service that runs in the same * process as the rest of the application, which is explicitly started and stopped * as desired.</p> * * <p>Note that this is implemented as an inner class only keep the sample * all together; typically this code would appear in some separate class. */ public static class Controller extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.local_service_controller); // Watch for button clicks. Button button = (Button)findViewById(R.id.start); button.setOnClickListener(mStartListener); button = (Button)findViewById(R.id.stop); button.setOnClickListener(mStopListener); } private OnClickListener mStartListener = new OnClickListener() { public void onClick(View v) { // Make sure the service is started. It will continue running // until someone calls stopService(). The Intent we use to find // the service explicitly specifies our service component, because // we want it running in our own process and don't want other // applications to replace it. startService(new Intent(Controller.this, LocalService.class)); } }; private OnClickListener mStopListener = new OnClickListener() { public void onClick(View v) { // Cancel a previous call to startService(). Note that the // service will not actually stop at this point if there are // still bound clients. stopService(new Intent(Controller.this, LocalService.class)); } }; } // ---------------------------------------------------------------------- /** * Example of binding and unbinding to the local service. * This demonstrates the implementation of a service which the client will * bind to, receiving an object through which it can communicate with the service.</p> * * <p>Note that this is implemented as an inner class only keep the sample * all together; typically this code would appear in some separate class. */ public static class Binding extends Activity { private boolean mIsBound; private LocalService mBoundService;
private ServiceConnection mConnection = new ServiceConnection() { public void onServiceConnected(ComponentName className, IBinder service) { // This is called when the connection with the service has been // established, giving us the service object we can use to // interact with the service. Because we have bound to a explicit // service that we know is running in our own process, we can // cast its IBinder to a concrete class and directly access it. mBoundService = ((LocalService.LocalBinder)service).getService();
// Tell the user about this for our demo. Toast.makeText(Binding.this, R.string.local_service_connected, Toast.LENGTH_SHORT).show(); } public void onServiceDisconnected(ComponentName className) { // This is called when the connection with the service has been // unexpectedly disconnected -- that is, its process crashed. // Because it is running in our same process, we should never // see this happen. mBoundService = null; Toast.makeText(Binding.this, R.string.local_service_disconnected, Toast.LENGTH_SHORT).show(); } };
void doBindService() { // Establish a connection with the service. We use an explicit // class name because we want a specific service implementation that // we know will be running in our own process (and thus won't be // supporting component replacement by other applications). bindService(new Intent(Binding.this, LocalService.class), mConnection, Context.BIND_AUTO_CREATE); mIsBound = true; }
肯定无效。你没办法控制一个activity被系统destory，但是系统destory你的时候，会调用onDestroy方法。
被标记为singleTask或者singleInstance的activity都在task的底部，在同一时间内，一个设备上不会有超过1个包含的这种类型的activity的task
一个被标记为singleInstance的activity在启动时，如果传过来的intent中有FLAG_ACTIVITY_NEW_TASK标记，则它会被放入一个新的task，除此之外，都与singleTask相同。详见android官方文档中dev guide中Application Fundamentals那部分，其中有讲的。要让自己的activity尽量不被销毁，只有想办法提高优先级，比如绑定一个运行中的service，或者虽然用户看不见了，但是它还是能影响的界面上显示的东西（这点不知道怎么做，文档中没详细说）。最变态的是让你的activity一直处于onCreate() onRestart() onStart() onResume()之一中因为当activity处于以上方法之一时是无法被kill的。
android 例子appdemos中一个本地service的例子。这里的activity优先级就高，但无论多高的优先级都不能保证不被销毁，除非是linux内核的东西。
看例子吧，不知道是不是有你想要的，看bingding那个内部类的东西就行了/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/package com.example.android.apis.app;import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import android.widget.Toast;// Need the following import to get access to the app resources, since this
// class is in a sub-package.
import com.example.android.apis.R;/**
* This is an example of implementing an application service that runs locally
* in the same process as the application. The {@link LocalServiceActivities.Controller}
* and {@link LocalServiceActivities.Binding} classes show how to interact with the
* service.
*
* <p>Notice the use of the {@link NotificationManager} when interesting things
* happen in the service. This is generally how background services should
* interact with the user, rather than doing something more disruptive such as
* calling startActivity().
*/public class LocalService extends Service {
private NotificationManager mNM; /**
* Class for clients to access. 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 LocalService.this;
}
}
@Override
public void onCreate() {
mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE); // Display a notification about us starting. We put an icon in the status bar.
showNotification();
} @Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i("LocalService", "Received start id " + startId + ": " + intent);
// We want this service to continue running until it is explicitly
// stopped, so return sticky.
return START_STICKY;
} @Override
public void onDestroy() {
// Cancel the persistent notification.
mNM.cancel(R.string.local_service_started); // Tell the user we stopped.
Toast.makeText(this, R.string.local_service_stopped, Toast.LENGTH_SHORT).show();
} @Override
public IBinder onBind(Intent intent) {
return mBinder;
} // This is the object that receives interactions from clients. See
// RemoteService for a more complete example.
private final IBinder mBinder = new LocalBinder(); /**
* Show a notification while this service is running.
*/
private void showNotification() {
// In this sample, we'll use the same text for the ticker and the expanded notification
CharSequence text = getText(R.string.local_service_started); // Set the icon, scrolling text and timestamp
Notification notification = new Notification(R.drawable.stat_sample, text,
System.currentTimeMillis()); // The PendingIntent to launch our activity if the user selects this notification
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
new Intent(this, LocalServiceActivities.Controller.class), 0); // Set the info for the views that show in the notification panel.
notification.setLatestEventInfo(this, getText(R.string.local_service_label),
text, contentIntent); // Send the notification.
// We use a layout id because it is a unique number. We use it later to cancel.
mNM.notify(R.string.local_service_started, notification);
}
}
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/package com.example.android.apis.app;import com.example.android.apis.R;import android.app.Activity;
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.Toast;public class LocalServiceActivities {
/**
* <p>Example of explicitly starting and stopping the local service.
* This demonstrates the implementation of a service that runs in the same
* process as the rest of the application, which is explicitly started and stopped
* as desired.</p>
*
* <p>Note that this is implemented as an inner class only keep the sample
* all together; typically this code would appear in some separate class.
*/
public static class Controller extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); setContentView(R.layout.local_service_controller); // Watch for button clicks.
Button button = (Button)findViewById(R.id.start);
button.setOnClickListener(mStartListener);
button = (Button)findViewById(R.id.stop);
button.setOnClickListener(mStopListener);
} private OnClickListener mStartListener = new OnClickListener() {
public void onClick(View v) {
// Make sure the service is started. It will continue running
// until someone calls stopService(). The Intent we use to find
// the service explicitly specifies our service component, because
// we want it running in our own process and don't want other
// applications to replace it.
startService(new Intent(Controller.this,
LocalService.class));
}
}; private OnClickListener mStopListener = new OnClickListener() {
public void onClick(View v) {
// Cancel a previous call to startService(). Note that the
// service will not actually stop at this point if there are
// still bound clients.
stopService(new Intent(Controller.this,
LocalService.class));
}
};
} // ---------------------------------------------------------------------- /**
* Example of binding and unbinding to the local service.
* This demonstrates the implementation of a service which the client will
* bind to, receiving an object through which it can communicate with the service.</p>
*
* <p>Note that this is implemented as an inner class only keep the sample
* all together; typically this code would appear in some separate class.
*/
public static class Binding extends Activity {
private boolean mIsBound;
private LocalService mBoundService;
private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
// This is called when the connection with the service has been
// established, giving us the service object we can use to
// interact with the service. Because we have bound to a explicit
// service that we know is running in our own process, we can
// cast its IBinder to a concrete class and directly access it.
mBoundService = ((LocalService.LocalBinder)service).getService();
// Tell the user about this for our demo.
Toast.makeText(Binding.this, R.string.local_service_connected,
Toast.LENGTH_SHORT).show();
} public void onServiceDisconnected(ComponentName className) {
// This is called when the connection with the service has been
// unexpectedly disconnected -- that is, its process crashed.
// Because it is running in our same process, we should never
// see this happen.
mBoundService = null;
Toast.makeText(Binding.this, R.string.local_service_disconnected,
Toast.LENGTH_SHORT).show();
}
};
void doBindService() {
// Establish a connection with the service. We use an explicit
// class name because we want a specific service implementation that
// we know will be running in our own process (and thus won't be
// supporting component replacement by other applications).
bindService(new Intent(Binding.this,
LocalService.class), mConnection, Context.BIND_AUTO_CREATE);
mIsBound = true;
}
void doUnbindService() {
if (mIsBound) {
// Detach our existing connection.
unbindService(mConnection);
mIsBound = false;
}
}
@Override
protected void onDestroy() {
super.onDestroy();
doUnbindService();
}
private OnClickListener mBindListener = new OnClickListener() {
public void onClick(View v) {
doBindService();
}
}; private OnClickListener mUnbindListener = new OnClickListener() {
public void onClick(View v) {
doUnbindService();
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); setContentView(R.layout.local_service_binding); // Watch for button clicks.
Button button = (Button)findViewById(R.id.bind);
button.setOnClickListener(mBindListener);
button = (Button)findViewById(R.id.unbind);
button.setOnClickListener(mUnbindListener);
}
}
}