如何解决Android：对主活动使用后退按钮会导致错误强制关闭
| 我有一个mainActivity是Customer.java，具有5个差异的listview。活动。当我点击它们时，我能够打开所有5个活动，但是当我按下后退按钮（设备后退按钮）返回到mainAcitivity时，会给我一个错误，您将在代码下方看到debug / logcat。我在主屏幕下有2个示例活动（注销和时钟输入）。 奖励：我想拥有的另一件事是，当单击“ clockinActivity”按钮时，我希望它将当前时间和日期发送到网络服务器（我的项目中已经有customhttp类）并自动返回到主屏幕。 我已经读过 http://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle http://android-developers.blogspot.com/2009/12/back-and-other-hard-keys-three-stories.html 而且这似乎不起作用@Override
public boolean onKeyDown(int keyCode,KeyEvent event)
{
if (keyCode == KeyEvent.KEYCODE_BACK)
{
//do smth
}
return super.onKeyDown(keyCode,event);
}
import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class Customer extends ListActivity
{
TextView selection;
CustomerListItem[] items = {
new CustomerListItem(\"Start Trip\",StartTripActivity.class),new CustomerListItem(\"Clock in\",ClockinActivity.class),new CustomerListItem(\"Customer Svc\",CustomerSvcActivity.class),new CustomerListItem(\"Independent Inspection\",InspectionActivity.class),new CustomerListItem(\"Pick Up\",PickUpActivity.class),new CustomerListItem(\"Log Out\",LogoutActivity.class)};
private TextView resultsTxt;
@Override
public void onCreate(Bundle icicle)
{
super.onCreate(icicle);
setContentView(R.layout.main);
setListAdapter(new ArrayAdapter<CustomerListItem>(
this,android.R.layout.simple_list_item_1,items));
selection = (TextView) findViewById(R.id.selection);
}
@Override
protected void onListItemClick(ListView l,View v,int position,long id)
{
super.onListItemClick(l,v,position,id);
final Intent intent = new Intent(this,items[position].getActivity());
startActivityForResult(intent,position);
}
@Override
protected void onActivityResult(int requestCode,int resultCode,Intent intent)
{
super.onActivityResult(requestCode,resultCode,intent);
if (resultCode == RESULT_OK)
{
// Perform different actions based on from which activity is
// the application returning:
switch (requestCode)
{
case 0:
// TODO: handle the return of the StartTripActivity
break;
case 1:
// TODO: handle the return of the ClockinActivity
break;
case 2:
// TODO: handle the return of the CustomerSvcActivity
case 3:
// TODO: handle the return of the InspectionActivity
break;
case 4:
// TODO: handle the return of the PickUpActivity
break;
case 5:
// TODO: handle the return of the LogoutActivity
break;
default:
break;
}
}
else if (resultCode == RESULT_CANCELED)
{
resultsTxt.setText(\"Canceled\");
}
}
}
import java.util.Date;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class ClockinActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.clockin);
Thread myThread = null;
Runnable runnable = new CountDownRunner();
myThread= new Thread(runnable);
myThread.start();
}
public void doWork() {
runOnUiThread(new Runnable() {
public void run() {
try{
TextView txtCurrentTime= (TextView)findViewById(R.id.lbltime);
Date dt = new Date();
int hours = dt.getHours();
int minutes = dt.getMinutes();
int seconds = dt.getSeconds();
String curTime = hours + \":\"+ minutes + \":\"+ seconds;
txtCurrentTime.setText(curTime);
}catch (Exception e) {
}
}
});
}
class CountDownRunner implements Runnable{
// @Override
public void run() {
while(!Thread.currentThread().isInterrupted()){
try {
doWork();
Thread.sleep(1000);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}catch(Exception e){
}
}
Button btn = (Button) findViewById(R.id.btn_OK);
//---event handler for the OK button---
btn.setOnClickListener(new View.OnClickListener()
{
public void onClick(View view) {
Intent data = new Intent();
//---get the EditText view---
// EditText txt_username =
// (EditText) findViewById(R.id.txt_username);
//---set the data to pass back---
// data.setData(Uri.parse(
// txt_username.getText().toString()));
setResult(RESULT_OK,data);
//---closes the activity---
finish();
}
});
}
}
}
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class LogoutActivity extends Activity {
private Button btnLogout;
private Button btnCancel;
private TextView lblResult;
private EditText code;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.logout);
code = (EditText)findViewById(R.id.codeout);
btnLogout = (Button) findViewById(R.id.submit);
btnCancel = (Button) findViewById(R.id.cancel);
lblResult = (TextView)findViewById(R.id.result);
btnLogout.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String logout = code.getText().toString();
if (logout.equals(\"99999\")){
lblResult.setText(\"Logout successful\");
Intent i = new Intent(getApplicationContext(),Login.class);
startActivity(i);
} else {
lblResult.setText(\"Logout failed\");
}
}
});
btnCancel.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(getApplicationContext(),Customer.class);
startActivity(i);
}
});
}}
解决方法
我通过使用下面的代码找到了答案。我不得不将代码放置在onCreate之前，将我一直在将代码放置在onCreate之后的错误。除非其他人有更好的建议，否则这似乎对我有用。即使这两个代码都起作用，我还是喜欢第一个代码，因为它会杀死当前活动'finish（）\'并返回到上一个屏幕，而第二个代码它将启动该活动并将两个活动都保留在堆栈中。
@Override
public boolean onKeyDown(int keyCode,KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
Pop(\"Back Button\");
Intent intent = new Intent();
setResult(RESULT_OK,intent);
finish();
return true;
}
return super.onKeyDown(keyCode,event);
}
@Override
public boolean onKeyDown(int keyCode,KeyEvent event)
{
//replaces the default \'Back\' button action
if(keyCode==KeyEvent.KEYCODE_BACK)
{
//do whatever you want the \'Back\' button to do
//as an example the \'Back\' button is set to start a new Activity named \'NewActivity\'
this.startActivity(new Intent(thisActivity.this,nextActivity.class));
}
return true;
}
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