如何显示一个对话框，以确认用户希望退出Android活动?

我一直试图在用户试图退出活动时显示“您想退出吗?”类型的对话框。

但是我找不到合适的API钩子。Activity.onUserLeaveHint()最初看起来很有希望，但我找不到一种方法来停止活动完成。

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小开

在Android 2.0+中，这看起来像:

@Override
public void onBackPressed() {
new AlertDialog.Builder(this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Closing Activity")
.setMessage("Are you sure you want to close this activity?")
.setPositiveButton("Yes", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}


})
.setNegativeButton("No", null)
.show();
}

在早期版本中，它看起来像:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
//Handle the back button
if(keyCode == KeyEvent.KEYCODE_BACK) {
//Ask the user if they want to quit
new AlertDialog.Builder(this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle(R.string.quit)
.setMessage(R.string.really_quit)
.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {


@Override
public void onClick(DialogInterface dialog, int which) {


//Stop the activity
YourClass.this.finish();
}


})
.setNegativeButton(R.string.no, null)
.show();


return true;
}
else {
return super.onKeyDown(keyCode, event);
}


}
小开 
@Override
public void onBackPressed() {
new AlertDialog.Builder(this)
.setMessage("Are you sure you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
ExampleActivity.super.onBackPressed();
}
})
.setNegativeButton("No", null)
.show();
}
小开

已修改@user919216代码..并使其与WebView兼容

@Override
public void onBackPressed() {
if (webview.canGoBack()) {
webview.goBack();


}
else
{
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
finish();
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
}


}
小开

如果你不确定调用“back”是否会退出应用程序，或者将用户带到另一个活动，你可以将上述答案包装在一个检查中，isTaskRoot()。如果您的主活动可以多次添加到后台堆栈，或者如果您正在操作后台堆栈历史，就会发生这种情况。

if(isTaskRoot()) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
YourActivity.super.onBackPressed;
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();


} else {
super.onBackPressed();
}
小开

我更喜欢双击后退按钮退出，而不是退出对话框。

在这个解决方案中，当第一次返回时，它会显示一个吐司，警告另一个回按将关闭应用程序。在这个例子中，不到4秒。

private Toast toast;
private long lastBackPressTime = 0;


@Override
public void onBackPressed() {
if (this.lastBackPressTime < System.currentTimeMillis() - 4000) {
toast = Toast.makeText(this, "Press back again to close this app", 4000);
toast.show();
this.lastBackPressTime = System.currentTimeMillis();
} else {
if (toast != null) {
toast.cancel();
}
super.onBackPressed();
}
}

令牌来自:http://www.androiduipatterns.com/2011/03/back-button-behavior.html

小开

我喜欢@GLee的方法，并像下面这样使用片段。

@Override
public void onBackPressed() {
if(isTaskRoot()) {
new ExitDialogFragment().show(getSupportFragmentManager(), null);
} else {
super.onBackPressed();
}
}

使用片段的对话框:

public class ExitDialogFragment extends DialogFragment {


@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
return new AlertDialog.Builder(getActivity())
.setTitle(R.string.exit_question)
.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
getActivity().finish();
}
})
.setNegativeButton(android.R.string.no, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
getDialog().cancel();
}
})
.create();
}
}
小开

使用λ:

    new AlertDialog.Builder(this).setMessage(getString(R.string.exit_msg))
.setTitle(getString(R.string.info))
.setPositiveButton(getString(R.string.yes), (arg0, arg1) -> {
moveTaskToBack(true);
finish();
})
.setNegativeButton(getString(R.string.no), (arg0, arg1) -> {
})
.show();

你还需要在gradle.build中设置支持java 8的级别语言:

compileOptions {
targetCompatibility 1.8
sourceCompatibility 1.8
}
小开

在中国，大多数App会通过“点击两次”确认退出:

boolean doubleBackToExitPressedOnce = false;


@Override
public void onBackPressed() {
if (doubleBackToExitPressedOnce) {
super.onBackPressed();
return;
}


this.doubleBackToExitPressedOnce = true;
Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();


new Handler().postDelayed(new Runnable() {


@Override
public void run() {
doubleBackToExitPressedOnce=false;
}
}, 2000);
}
小开

首先从onbackPressed()方法中删除super.onBackPressed();:

@Override
public void onBackPressed() {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
MyActivity.this.finish();
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();


}
小开

另一个替代方法是在第一次回按时显示__ABC0/Snackbar，要求再次回按退出，这比显示AlertDialog来确认用户是否想退出应用程序要少得多。

你可以使用DoubleBackPress Android Library来实现这一点，只需几行代码。示例GIF显示类似的行为。

首先，将依赖项添加到应用程序中:

dependencies {
implementation 'com.github.kaushikthedeveloper:double-back-press:0.0.1'
}

接下来，在您的活动中，实现所需的行为。

// set the Toast to be shown on FirstBackPress (ToastDisplay - builtin template)
// can be replaced by custom action (new FirstBackPressAction{...})
FirstBackPressAction firstBackPressAction = new ToastDisplay().standard(this);


// set the Action on DoubleBackPress
DoubleBackPressAction doubleBackPressAction = new DoubleBackPressAction() {
@Override
public void actionCall() {
// TODO : Exit the application
finish();
System.exit(0);
}
};


// setup DoubleBackPress behaviour : close the current Activity
DoubleBackPress doubleBackPress = new DoubleBackPress()
.withDoublePressDuration(3000)     // msec - wait for second back press
.withFirstBackPressAction(firstBackPressAction)
.withDoubleBackPressAction(doubleBackPressAction);

最后，将此设置为背压的行为。

@Override
public void onBackPressed() {
doubleBackPress.onBackPressed();
}
小开 
Just put this code in your first activity


@Override
public void onBackPressed() {
if (drawerLayout.isDrawerOpen(GravityCompat.END)) {
drawerLayout.closeDrawer(GravityCompat.END);
}
else {
// if your using fragment then you can do this way
int fragments = getSupportFragmentManager().getBackStackEntryCount();
if (fragments == 1) {
new AlertDialog.Builder(this)
.setMessage("Are you sure you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
finish();
}
})
.setNegativeButton("No", null)
.show();




} else {
if (getFragmentManager().getBackStackEntryCount() > 1) {
getFragmentManager().popBackStack();
} else {


super.onBackPressed();
}
}
}
}

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