当我在android中按回为啥不退出应用程序？
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【中文标题】当我在android中按回为啥不退出应用程序？【英文标题】：when I press back in android why not exit the application?当我在android中按回为什么不退出应用程序？ 【发布时间】：2016-08-21 03:05:31 【问题描述】：我的主要活动是使用谷歌登录的 LoginActivity，当用户登录时将定向到 MapsActivity，当用户在 MapsActivity 中单击“返回”时，我希望用户退出应用程序，但现在为什么单击“返回”时应用程序刚刚再次打开MapsActvity 让用户无法退出？
LoginActivity.java
package com.emergency;
/**
* Created by Eggy on 4/17/2016.
*/
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import com.google.android.gms.auth.api.Auth;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.auth.api.signin.GoogleSignInResult;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.SignInButton;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.OptionalPendingResult;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.common.api.Status;
/**
* Activity to demonstrate basic retrieval of the Google user's ID, email address, and basic
* profile.
*/
public class LoginActivity extends AppCompatActivity implements
GoogleApiClient.OnConnectionFailedListener,
View.OnClickListener
private static final String TAG = "SignInActivity";
private static final int RC_SIGN_IN = 9001;
private GoogleApiClient mGoogleApiClient;
private ProgressDialog mProgressDialog;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
// Button listeners
findViewById(R.id.sign_in_button).setOnClickListener(this);
// [START configure_signin]
// Configure sign-in to request the user's ID, email address, and basic
// profile. ID and basic profile are included in DEFAULT_SIGN_IN.
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
.requestEmail()
.build();
// [END configure_signin]
// [START build_client]
// Build a GoogleApiClient with access to the Google Sign-In API and the
// options specified by gso.
mGoogleApiClient = new GoogleApiClient.Builder(this)
.enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
.addApi(Auth.GOOGLE_SIGN_IN_API, gso)
.build();
// [END build_client]
// [START customize_button]
// Customize sign-in button. The sign-in button can be displayed in
// multiple sizes and color schemes. It can also be contextually
// rendered based on the requested scopes. For example. a red button may
// be displayed when Google+ scopes are requested, but a white button
// may be displayed when only basic profile is requested. Try adding the
// Scopes.PLUS_LOGIN scope to the GoogleSignInOptions to see the
// difference.
SignInButton signInButton = (SignInButton) findViewById(R.id.sign_in_button);
signInButton.setSize(SignInButton.SIZE_STANDARD);
signInButton.setScopes(gso.getScopeArray());
// [END customize_button]
@Override
public void onStart()
super.onStart();
OptionalPendingResult<GoogleSignInResult> opr = Auth.GoogleSignInApi.silentSignIn(mGoogleApiClient);
if (opr.isDone())
// If the user's cached credentials are valid, the OptionalPendingResult will be "done"
// and the GoogleSignInResult will be available instantly.
Log.d(TAG, "Got cached sign-in");
GoogleSignInResult result = opr.get();
handleSignInResult(result);
else
// If the user has not previously signed in on this device or the sign-in has expired,
// this asynchronous branch will attempt to sign in the user silently. Cross-device
// single sign-on will occur in this branch.
showProgressDialog();
opr.setResultCallback(new ResultCallback<GoogleSignInResult>()
@Override
public void onResult(GoogleSignInResult googleSignInResult)
hideProgressDialog();
handleSignInResult(googleSignInResult);
);
// [START onActivityResult]
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data)
super.onActivityResult(requestCode, resultCode, data);
// Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
if (requestCode == RC_SIGN_IN)
GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
handleSignInResult(result);
// [END onActivityResult]
// [START handleSignInResult]
private void handleSignInResult(GoogleSignInResult result)
Log.d(TAG, "handleSignInResult:" + result.isSuccess());
if (result.isSuccess())
// Signed in successfully, show authenticated UI.
GoogleSignInAccount acct = result.getSignInAccount();
updateUI(true);
else
// Signed out, show unauthenticated UI.
updateUI(false);
// [END handleSignInResult]
// [START signIn]
private void signIn()
Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
startActivityForResult(signInIntent, RC_SIGN_IN);
// [END signIn]
// [START signOut]
private void signOut()
Auth.GoogleSignInApi.signOut(mGoogleApiClient).setResultCallback(
new ResultCallback<Status>()
@Override
public void onResult(Status status)
// [START_EXCLUDE]
updateUI(false);
// [END_EXCLUDE]
);
// [END signOut]
// [START revokeAccess]
private void revokeAccess()
Auth.GoogleSignInApi.revokeAccess(mGoogleApiClient).setResultCallback(
new ResultCallback<Status>()
@Override
public void onResult(Status status)
// [START_EXCLUDE]
updateUI(false);
// [END_EXCLUDE]
);
// [END revokeAccess]
@Override
public void onConnectionFailed(ConnectionResult connectionResult)
// An unresolvable error has occurred and Google APIs (including Sign-In) will not
// be available.
Log.d(TAG, "onConnectionFailed:" + connectionResult);
private void showProgressDialog()
if (mProgressDialog == null)
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setMessage(getString(R.string.loading));
mProgressDialog.setIndeterminate(true);
mProgressDialog.show();
private void hideProgressDialog()
if (mProgressDialog != null && mProgressDialog.isShowing())
mProgressDialog.hide();
private void updateUI(boolean signedIn)
if (signedIn)
Intent i = new Intent(LoginActivity.this, MapsActivity.class);
startActivity(i);
else
findViewById(R.id.sign_in_button).setVisibility(View.VISIBLE);
@Override
public void onClick(View v)
switch (v.getId())
case R.id.sign_in_button:
signIn();
break;
MapsActivity.java
package com.emergency;
import android.content.Intent;
import android.location.Location;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesNotAvailableException;
import com.google.android.gms.common.GooglePlayServicesRepairableException;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.places.Place;
import com.google.android.gms.location.places.Places;
import com.google.android.gms.location.places.ui.PlacePicker;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener
private GoogleMap mMap;
int PLACE_PICKER_REQUEST = 1;
GoogleApiClient mGoogleApiClient;
boolean search=false;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
mGoogleApiClient = new GoogleApiClient
.Builder(this)
.addApi(Places.GEO_DATA_API)
.addApi(Places.PLACE_DETECTION_API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
public void onSearch(View view)
PlacePicker.IntentBuilder builder = new PlacePicker.IntentBuilder();
try
startActivityForResult(builder.build(this), PLACE_PICKER_REQUEST);
catch (GooglePlayServicesRepairableException e)
e.printStackTrace();
catch (GooglePlayServicesNotAvailableException e)
e.printStackTrace();
/**
* Manipulates the map once available.
* This callback is triggered when the map is ready to be used.
* This is where we can add markers or lines, add listeners or move the camera. In this case,
* we just add a marker near Sydney, Australia.
* If Google Play services is not installed on the device, the user will be prompted to install
* it inside the SupportMapFragment. This method will only be triggered once the user has
* installed Google Play services and returned to the app.
*/
@Override
public void onMapReady(GoogleMap googleMap)
mMap = googleMap;
mMap.setTrafficEnabled(true);
mMap.setMyLocationEnabled(true);
mMap.setOnMyLocationChangeListener(onMyLocationChangeListener);
protected void onActivityResult(int requestCode, int resultCode, Intent data)
if (requestCode == PLACE_PICKER_REQUEST)
if (resultCode == RESULT_OK)
Place place = PlacePicker.getPlace(data, this);
LatLng latLng = new LatLng(place.getLatLng().latitude,place.getLatLng().longitude);
mMap.addMarker(new MarkerOptions().position(latLng).title(place.getAddress().toString()));
mMap.animateCamera(CameraUpdateFactory.newLatLng(latLng));
mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mMap.animateCamera(CameraUpdateFactory.zoomTo(15));
private GoogleMap.OnMyLocationChangeListener onMyLocationChangeListener = new GoogleMap.OnMyLocationChangeListener()
@Override
public void onMyLocationChange(Location location)
if(!search)
mMap.moveCamera(CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(), location.getLongitude())));
mMap.animateCamera(CameraUpdateFactory.zoomTo(15));
search=true;
;
@Override
public void onConnected(Bundle bundle)
@Override
public void onConnectionSuspended(int i)
@Override
public void onConnectionFailed(ConnectionResult connectionResult)
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.emergency"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk
android:minSdkVersion="15"
android:targetSdkVersion="17" />
<permission
android:name="com.emergency.permission.MAPS_RECEIVE"
android:protectionLevel="signature" />
<uses-permission android:name="com.emergency.permission.MAPS_RECEIVE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<!-- To access accounts configured on device -->
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<!-- To use account credentials -->
<uses-permission android:name="android.permission.USE_CREDENTIALS" />
<uses-feature
android:glEsVersion="0x00020000"
android:required="true" />
//OpenGL ES version 2
<android:uses-permission android:name="android.permission.READ_PHONE_STATE" />
<android:uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/CustomActionBarTheme">
<meta-data
android:name="com.google.android.geo.API_KEY"
android:value="@string/google_maps_key" />
<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
<activity
android:name=".splashscreen"
android:label="@string/app_name"
android:noHistory="true"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!-- Main activity -->
<activity
android:name=".MapsActivity"
android:label="@string/title_activity_maps">
</activity>
<activity
android:name=".LoginActivity"
android:screenOrientation="portrait"
android:theme="@style/Theme.AppCompat"/>
</application>
</manifest>
【问题讨论】：
【参考方案1】：试试这个代码
public void onBackPressed()
moveTaskToBack(true);
【讨论】：
嗯？我们甚至应该把它放在哪里？对于想知道为什么会发生这种情况的我们来说，OP 问题的根本问题/根源是什么？以上是关于当我在android中按回为啥不退出应用程序？的主要内容，如果未能解决你的问题，请参考以下文章
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