[英]Android Service-Activity 2 way communication
in my team's Android application I have a service running from boot which communicates with a server to perform operations such as logging in, registering, chatting between phones and updating the phone database. 在我的团队的Android应用程序中,我有一个从启动运行的服务,它与服务器通信以执行诸如登录,注册,在电话之间聊天和更新电话数据库等操作。
I need to make my service communicate with the activity bi-directionally: for example I am working on the login activity at the moment and the username and passwords are Strings taken from a text field on the app screen and I have been able to pass them to the service for it to send an authorisation command to the server. 我需要让我的服务与双向活动进行通信:例如,我正在处理登录活动,用户名和密码是从应用程序屏幕上的文本字段中获取的字符串,我已经能够通过它们向服务器发送授权命令到服务器。
public void loginPressed(View v){
usernameStr = usernameField.getText().toString();
passwordStr = passwordField.getText().toString();
if (!bound) return;
Bundle b = new Bundle();
Message msg = Message.obtain(null, ChatService.LOGIN);
try {
b.putString("username", usernameStr);
b.putString("password", passwordStr);
msg.setData(b);
messenger.send(msg);
}
catch (RemoteException e) {
}
This works as I would have expected. 这可以像我预期的那样工作。 When the server responds with a message saying whether or not the login was sucessful, I need it to pass a message back to the activity so that I can start the main activity if succesful or prompt for re-entry if not.
当服务器响应一条消息,说明登录是否成功时,我需要它将消息传递回活动,以便我可以启动主要活动,如果成功或提示重新进入,如果没有。
I tried to use the msg.replyTo field to get the return messenger to send the information back, but when I run the app it force closes with a null pointer exception and I have no idea why this is happening. 我尝试使用msg.replyTo字段来获取返回信使以发回信息,但是当我运行应用程序时,它会以空指针异常关闭,我不知道为什么会发生这种情况。 Here is the code that seems to be the culprit:
这是代码似乎是罪魁祸首:
private class IncomingHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch(msg.what) {
case LOGIN:
Bundle b = msg.getData();
String username = b.getString("username");
String password = b.getString("password");
String loginMessage = TCPCall.login(username, password);
connection.sendMessage(loginMessage);
String loginReturn = connection.retrieveMessage();
Message m;
Scanner s = new Scanner(loginReturn);
s.useDelimiter(",");
String c = s.next();
String status = s.next();
String message = s.next();
if (status.equals("OK")) {
m = Message.obtain(null, LoginActivity.OK);
try {
msg.replyTo.send(m);
} catch (RemoteException e) {}
}
else {
m = Message.obtain(null, LoginActivity.ERR);
try {
msg.replyTo.send(m);
} catch (RemoteException e) {}
}
break;
The null pointer seems to be coming from the 空指针似乎来自于
msg.replyTo.send(m);
line of code in both cases (login succesful and login failed) 两种情况下的代码行(登录成功和登录失败)
Any help to fix this problem would be greatly appreciated :) 任何帮助解决这个问题将不胜感激:)
As Gregg points out in the comments. 正如格雷格在评论中指出的那样。 You need to set
msg.replyTo = messenger;
你需要设置
msg.replyTo = messenger;
int he place where you send the original message. int他发送原始邮件的地方。
An example can be found here: http://www.survivingwithandroid.com/2014/01/android-bound-service-ipc-with-messenger.html 可以在此处找到一个示例: http : //www.survivingwithandroid.com/2014/01/android-bound-service-ipc-with-messenger.html
I think you forgot to send response to Login Activity by bundle from Service.
我想你忘了通过服务包发送对Login Activity的响应。 So, i made some changes in Messenger Service
所以,我在Messenger Service中做了一些更改
define one global variable and made some changes in Incoming Handler 定义一个全局变量并在Incoming Handler中进行一些更改
static final int LOGIN_STATUS = 1;
private class IncomingHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch(msg.what) {
case LOGIN:
Bundle b = msg.getData();
String username = b.getString("username");
String password = b.getString("password");
String loginMessage = TCPCall.login(username, password);
connection.sendMessage(loginMessage);
String loginReturn = connection.retrieveMessage();
Message m = Message.obtain(null, LOGIN_STATUS);
Scanner s = new Scanner(loginReturn);
s.useDelimiter(",");
String c = s.next();
String status = s.next();
String message = s.next();
if (status.equals("OK")) {
b.putString("responseC",c);
b.putString("responseStatus",status);
b.putString("responseMessage",message)
m.setData(b);
try {
msg.replyTo.send(m);
} catch (RemoteException e) {}
}
else {
/*if something is wrong with username and password you can put
a toast*/
}
break;
Now we have to catch this response in our LoginActivity and take IncomingHandler in Login Activity also
现在我们必须在LoginActivity中捕获此响应,并在Login Activity中使用IncomingHandler
class IncomingHandler extends Handler{
@Override
public void handleMessage(Message msg) {
switch (msg.what){
case ChatService.LOGIN_STATUS:
String C = msg.getData().getString("responseC");
String Status = msg.getData().getString("responseStatus");
String Message = msg.getData().getString("responseMessage");
//Here is your response in LoginActivity, enjoy!!!
break;
default:
super.handleMessage(msg);
}
}
}
final Messenger mMessenger = new Messenger(new IncomingHandler());
public void loginPressed(View v){
usernameStr = usernameField.getText().toString();
passwordStr = passwordField.getText().toString();
if (!bound) return;
Bundle b = new Bundle();
Message msg = Message.obtain(null, ChatService.LOGIN_SATUS,0,0);
try {
b.putString("username", usernameStr);
b.putString("password", passwordStr);
msg.setData(b);
msg.replyTo = mMessenger;
messenger.send(msg);
}
catch (RemoteException e) {
// In this case the service has crashed before we could even
// do anything with it; we can count on soon being
// disconnected (and then reconnected if it can be restarted)
// so there is no need to do anything here.
}
This code is working perfectly, hope it will help you, Thanks
这段代码工作正常,希望它会对你有所帮助,谢谢
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