我的应用程序出现问题，当我的应用程序刷新或加载缓慢的互联网连接时...活动总是销毁，或者＃34;不幸（姓名）停止＆＃34;我怎样才能阻止Force关闭我的活动。我使用Asynctask和JSON文件从PHP中获取数据。这是我的代码：
package com.example.this;
import android.app.Activity;
import android.app.ActivityManager;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class Frontpane extends Activity {
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ( keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
onBackPressed();
}
return super.onKeyDown(keyCode, event);
}
@Override
public void onBackPressed() {
return;
}
Button Loginbutton;
Button exitButton;
EditText username=null;
EditText password=null;
EditText checker;
String Username1;
String Password1;
/** For database connection**/
private static String url = "http://1.1.1.1/radarMonitoring/api/retrieveacc.php";
private static final String TAG_REGISTEREDACCOUNTS = "RegisteredAccounts";
private static final String TAG_ACCNUM = "Acc_Num";
private static final String TAG_USEREG = "User_NameReg";
private static final String TAG_PASSREG = "Pass_WordReg";
JSONArray accnt = null;
String cntb;
String cnta;
String can;
String cbn;
int usncnt;
int pswcnt;
ArrayList<HashMap<String, String>> accntList;
/** For database connection**/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.front);
Toast.makeText(Frontpane.this, "Please Login to Continue.", Toast.LENGTH_SHORT).show();
exitButton = (Button) findViewById(R.id.button);
username=(EditText)findViewById(R.id.username);
password=(EditText)findViewById(R.id.password);
// checker=(EditText)findViewById(R.id.editText1);
exitButton.setOnClickListener(button);
addButtonListener();
/**array of usernames and pw **/
accntList = new ArrayList<HashMap<String, String>>();
/**array of usernames and pw **/
}
private class GetContacts extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
accnt = jsonObj.getJSONArray(TAG_REGISTEREDACCOUNTS);
// looping through All Contacts
for (int i = 0; i < accnt.length(); i++) {
int l;
JSONObject c = accnt.getJSONObject(i);
// String an = c.getString(TAG_ACCNUM);
String unr = c.getString(TAG_USEREG);
// String pwr = c.getString(TAG_PASSREG);
// tmp hashmap for single contac
HashMap<String, String> acc = new HashMap<String, String>();
// adding each child node to HashMap key => value
// acc.put(TAG_ACCNUM, an);
acc.put(TAG_USEREG, unr);
// acc.put(TAG_PASSREG, pwr);
if(unr.equals(Username1)){
usncnt = i;
can = unr;
}
// adding contact to contact list
accntList.add(acc);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
Toast.makeText(Frontpane.this,"Please Check Your Internet Connection", Toast.LENGTH_SHORT).show();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
/**
* Updating parsed JSON data into ListView
* */
cnta = can;
if(Username1.isEmpty()==false){
if(Password1.isEmpty()){
Toast.makeText(Frontpane.this, "Please Enter Password!", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
else{
if(cnta!=null){
new GetPAss().execute();
}
else{
Toast.makeText(Frontpane.this, "Not Registered or Check your Internet Connection..", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
}
}
else{
Toast.makeText(Frontpane.this, "Please Enter Username!", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
}
}
private class GetPAss extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
accnt = jsonObj.getJSONArray(TAG_REGISTEREDACCOUNTS);
// looping through All Contacts
for (int i = 0; i < accnt.length(); i++) {
int l;
JSONObject c = accnt.getJSONObject(i);
// String an = c.getString(TAG_ACCNUM);
//String unr = c.getString(TAG_USEREG);
String pwr = c.getString(TAG_PASSREG);
// tmp hashmap for single contac
HashMap<String, String> acc = new HashMap<String, String>();
// adding each child node to HashMap key => value
// acc.put(TAG_ACCNUM, an);
// acc.put(TAG_USEREG, unr);
acc.put(TAG_PASSREG, pwr);
if(pwr.equals(Password1)){
pswcnt = i;
cbn = pwr;
}
// adding contact to contact list
accntList.add(acc);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
Toast.makeText(Frontpane.this,"Please Check Your Internet Connection", Toast.LENGTH_SHORT).show();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
/**
* Updating parsed JSON data into ListView
* */
cntb = cbn;
if(Username1.isEmpty()){
Toast.makeText(Frontpane.this, "Please Enter Username!", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
else{
/* Toast.makeText(Frontpane.this, "meron", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null); */
if(cntb!=null){
if((pswcnt>=0)&&(usncnt>=0)){
if(pswcnt==usncnt){
Intent intent = new Intent(Frontpane.this,MyActivity.class);
startActivity(intent);
Toast.makeText(Frontpane.this, "Login Successful!", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
else{
Toast.makeText(Frontpane.this, "Username and Password does not match, Please Try Again! ", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
}
}
else{
Toast.makeText(Frontpane.this, "Wrong Password, Please Try Again! ", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
}
}
}
DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
switch (which){
case DialogInterface.BUTTON_POSITIVE:
ActivityManager activityManager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
activityManager.killBackgroundProcesses("com.example.RadarOperationMonitoringSystem");
int pid = android.os.Process.myPid();
android.os.Process.killProcess(pid);
// Method 2
System.exit(0);
break;
case DialogInterface.BUTTON_NEGATIVE:
break;
}
}
};
public void addButtonListener() {
Loginbutton = (Button) findViewById(R.id.buttonLogin);
Loginbutton.setOnClickListener(new OnClickListener() {
public void onClick(View view) {
Username1 = username.getText().toString();
Password1 = password.getText().toString();
new GetContacts().execute();
Toast.makeText(Frontpane.this, "Please Wait.. Verifying User Log-in. ", Toast.LENGTH_SHORT).show();
}
});
}
OnClickListener button = new OnClickListener() {
public void onClick(View v) {
AlertDialog.Builder builder = new AlertDialog.Builder(Frontpane.this);
builder.setMessage("Are you sure want to exit?").setPositiveButton("Yes", dialogClickListener)
.setNegativeButton("No", dialogClickListener).show();
}
};
}
答案 0 :(得分：1)
通过从doInBackground方法返回适当的值，在后执行中执行此操作。所有与UI相关的代码都应该在ui线程中运行。
Toast.makeText(Frontpane.this,"Please Check Your Internet Connection", Toast.LENGTH_SHORT).show();
更新
你必须做这样的事情
private class GetContacts extends AsyncTask<Void, Void, Boolean> {
@Override
protected Boolean doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
accnt = jsonObj.getJSONArray(TAG_REGISTEREDACCOUNTS);
// looping through All Contacts
for (int i = 0; i < accnt.length(); i++) {
int l;
JSONObject c = accnt.getJSONObject(i);
// String an = c.getString(TAG_ACCNUM);
String unr = c.getString(TAG_USEREG);
// String pwr = c.getString(TAG_PASSREG);
// tmp hashmap for single contac
HashMap<String, String> acc = new HashMap<String, String>();
// adding each child node to HashMap key => value
// acc.put(TAG_ACCNUM, an);
acc.put(TAG_USEREG, unr);
// acc.put(TAG_PASSREG, pwr);
if(unr.equals(Username1)){
usncnt = i;
can = unr;
}
// adding contact to contact list
accntList.add(acc);
}
} catch (JSONException e) {
e.printStackTrace();
return false;
}
return true;
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
///Toast.makeText(Frontpane.this,"Please Check Your Internet Connection", Toast.LENGTH_SHORT).show();
return false;
}
}
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
// Dismiss the progress dialog
/**
* Updating parsed JSON data into ListView
* */
if(!result)
{
// add here your message
Toast.makeText(Frontpane.this,"Please Check Your Internet Connection", Toast.LENGTH_SHORT).show();
return;
}
cnta = can;
if(Username1.isEmpty()==false){
if(Password1.isEmpty()){
Toast.makeText(Frontpane.this, "Please Enter Password!", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
else{
if(cnta!=null){
new GetPAss().execute();
}
else{
Toast.makeText(Frontpane.this, "Not Registered or Check your Internet Connection..", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
}
}
else{
Toast.makeText(Frontpane.this, "Please Enter Username!", Toast.LENGTH_SHORT).show();
username.setText(null, null);
password.setText(null, null);
}
}
答案 1 :(得分：0)
执行asynctask的工作流程如下
onPreExecute()
doInBackground(Params...)
onProgressUpdate(Progress...)
onPostExecute(Result)
除了doInBackground（Params ...）之外，可以在这些方法上调用UI代码。 UI工作应该推迟到onPostExecute（Result）。
似乎doInbackground中的toast消息是在代码中的异常之后触发的。