这个类有什么问题，我收到错误，因为"无法在未调用 Looper.prepare（） 的线程中创建处理程序"，并且错误指向姿势 MessageSend 的执行。
public class ComposeActivity extends Activity {
String receiver,subject,message;
TextView compose_to;
EditText compose_subject;
TextView compose_msg_label;
EditText compose_message;
TextView compose_error;
Button send_pm;
ConnectionDetector cd ;
AlertDialogManager alert;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_compose);
getActionBar().setDisplayHomeAsUpEnabled(true); // Put the back button in title
Bundle bundle = getIntent().getExtras();
/*
* Instantiate objects
*/
cd = new ConnectionDetector(getApplicationContext()); // Connection Detector
alert = new AlertDialogManager(); // Alert Dialog
/*
* Assign view to variable
*/
compose_to = (TextView)findViewById(R.id.compose_to);
compose_subject = (EditText)findViewById(R.id.compose_subject);
compose_msg_label = (TextView)findViewById(R.id.compose_message_label);
compose_message = (EditText)findViewById(R.id.compose_message);
compose_error = (TextView)findViewById(R.id.compose_error);
send_pm = (Button)findViewById(R.id.send_pm);
/*
* Check for the passed receiver
*/
if(bundle != null){
receiver = bundle.getString("to");
compose_to.setText(receiver);
}
/*
* send_pm button click
*/
send_pm.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View arg0) {
subject = compose_subject.getText().toString();
message = compose_message.getText().toString();
/*
* check emptyness
*/
if(!subject.equals("") && !message.equals("")){
if(cd.isConnectingToInternet()){
//Toast.makeText(getApplicationContext(),"Correct", Toast.LENGTH_SHORT).show();
new MessageSend().execute();
}else{
alert.showAlertDialog(ComposeActivity.this, getResources().getString(R.string.connection_error_head), getResources().getString(R.string.connection_error), null);
}
}else if(subject.equals("")){
Toast.makeText(getApplicationContext(), getResources().getString(R.string.empty_subject), Toast.LENGTH_SHORT).show();
}else if(message.equals("")){
Toast.makeText(getApplicationContext(), getResources().getString(R.string.empty_message), Toast.LENGTH_SHORT).show();
}else{
Toast.makeText(getApplicationContext(), getResources().getString(R.string.toast_blank_input), Toast.LENGTH_SHORT).show();
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.compose, menu);
return true;
}
/*
*
*/
private class MessageSend extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
String loc;
@Override
protected void onPreExecute() {
super.onPreExecute();
Bundle bundle = getIntent().getExtras();
//id = bundle.getString("siteid");
pDialog = new ProgressDialog(ComposeActivity.this);
pDialog.setMessage("Sending Message ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
//user = db.getUserDetails();
UserFunctions userFunction = new UserFunctions();
//JSONObject json = userFunction.deleteSite(id);
return null;
}
@Override
protected void onPostExecute(JSONObject json) {
try {
if(json.has("success_msg")){
pDialog.dismiss();
Intent intent = new Intent(ComposeActivity.this,SitePage.class);
startActivity(intent);
Toast.makeText(getApplicationContext(), json.getString("success_msg"), Toast.LENGTH_SHORT).show();
}else{
pDialog.dismiss();
String err = json.getString("error_msg");
Toast.makeText(getApplicationContext(), err, Toast.LENGTH_SHORT).show();
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
这是我的日志猫
02-21 22:32:10.655: E/AndroidRuntime(2403): FATAL EXCEPTION: main
02-21 22:32:10.655: E/AndroidRuntime(2403): java.lang.NullPointerException
02-21 22:32:10.655: E/AndroidRuntime(2403): at com.Creators.biotrack.ComposeActivity$MessageSend.onPostExecute(ComposeActivity.java:131)
02-21 22:32:10.655: E/AndroidRuntime(2403): at com.Creators.biotrack.ComposeActivity$MessageSend.onPostExecute(ComposeActivity.java:1)
02-21 22:32:10.655: E/AndroidRuntime(2403): at android.os.AsyncTask.finish(AsyncTask.java:631)
02-21 22:32:10.655: E/AndroidRuntime(2403): at android.os.AsyncTask.access$600(AsyncTask.java:177)
02-21 22:32:10.655: E/AndroidRuntime(2403): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
02-21 22:32:10.655: E/AndroidRuntime(2403): at android.os.Handler.dispatchMessage(Handler.java:99)
02-21 22:32:10.655: E/AndroidRuntime(2403): at android.os.Looper.loop(Looper.java:137)
02-21 22:32:10.655: E/AndroidRuntime(2403): at android.app.ActivityThread.main(ActivityThread.java:5103)
02-21 22:32:10.655: E/AndroidRuntime(2403): at java.lang.reflect.Method.invokeNative(Native Method)
02-21 22:32:10.655: E/AndroidRuntime(2403): at java.lang.reflect.Method.invoke(Method.java:525)
02-21 22:32:10.655: E/AndroidRuntime(2403): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-21 22:32:10.655: E/AndroidRuntime(2403): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-21 22:32:10.655: E/AndroidRuntime(2403): at dalvik.system.NativeStart.main(Native Method)
毕竟.我在代码中做了一些小的更改，它奏效了。我做了以下更改。
-
在顶级类上声明 pDialog，即
public class ComposeActivity extends Activity { public ProgressDialog pDialog; String receiver,subject,message; TextView compose_to; .................... ................. -
我在吐司上用了
ComposeActivity.this而不是getApplicationContext()protected void onPostExecute(JSONObject json)
问题解决了。但是我仍然不明白为什么以前的实现不起作用，因为它正在处理其他一些类。