Question

编辑：我知道了问题所在。我有2个意图（一个用于当用户登录时，如果用户已经登录则返回一个）我只是在改变第一个从未真正存在过的跑。我对此感到无能为力，但感谢所有尝试提供帮助的人。

因此，我有一个登录活动和一个主活动，我希望从后堆栈中删除该登录活动，以便用户一旦登录就无法返回该活动。我知道这应该很简单而且我已经尝试了很多方法，但是仍然无法正常工作。我已经尝试了所有3个“标志”，如下所示：

intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);

，并一次添加一个。我还尝试过将finish()或finishAffinity()的行放在意图行周围，但仍然没有运气。我在做什么错了？

以下是与意图有关的代码：

Intent intent = new Intent(LoginActivity.this, MainActivity.class);
startActivity(intent);

编辑：请求的代码：

AndroidManifest.xml ：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.music">

    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:networkSecurityConfig="@xml/network_security_config"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        android:usesCleartextTraffic="true">
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main"/>
        <activity
            android:name=".RegisterActivity"
            android:label="" />
        <activity
            android:name=".LoginActivity"
            android:label="">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

LoginActivity.java ：

package com.example.music;

import androidx.annotation.StringRes;
import androidx.appcompat.app.AppCompatActivity;

import android.app.ActivityOptions;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
import android.util.Pair;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.android.volley.RequestQueue;
import com.android.volley.RetryPolicy;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;
import com.example.music.ui.Token;
import com.google.gson.Gson;

import org.json.JSONException;
import org.json.JSONObject;

public class LoginActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        GlobalVariables globalVariables = new GlobalVariables();

        final TextView title = findViewById(R.id.title);
        final EditText email = findViewById(R.id.emailInput);
        final EditText password = findViewById(R.id.passwordInput);
        final Button signUp = findViewById(R.id.signUp);
        Button signIn = findViewById(R.id.signIn);

        //check if token exists
        SharedPreferences sharedPreferences = getSharedPreferences("StoredValues", MODE_PRIVATE);
        String token = sharedPreferences.getString("token", "null");
        if(!token.equals("null")){
            globalVariables.setToken(token);
            Intent myIntent = new Intent(LoginActivity.this, MainActivity.class);
            LoginActivity.this.startActivity(myIntent);
        }

        signUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent openRegisterActivity = new Intent(LoginActivity.this, RegisterActivity.class);

                Pair[] pairs = new Pair[4];
                pairs[0] = new Pair<View, String>(title, "titleTransition");
                pairs[1] = new Pair<View, String>(email, "emailTransition");
                pairs[2] = new Pair<View, String>(password, "passwordTransition");
                pairs[3] = new Pair<View, String>(signUp, "signUpTransition");

                ActivityOptions options = ActivityOptions.makeSceneTransitionAnimation(LoginActivity.this, pairs);
                getWindow().setExitTransition(null);
                startActivity(openRegisterActivity, options.toBundle());
            }
        });

        signIn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(final View view) {
                Utils utils = new Utils(getApplicationContext());
                GlobalVariables globalVariables = new GlobalVariables();
                if(email.getText().toString().equals("") || password.getText().toString().equals("")){
                    //at least one input is empty
                    utils.DisplayPopup(view, getResources().getString(R.string.empty_input_box));
                }
                else{
                    //everything is good to go
                    String url = globalVariables.getIPAddress() + "login/";

                    RequestQueue requestQueue = Volley.newRequestQueue(getApplicationContext());

                    try {
                        JSONObject jsonObject = new JSONObject();
                        jsonObject.put("username", email.getText().toString());
                        jsonObject.put("password", password.getText().toString());

                        JsonObjectRequest objectRequest = new JsonObjectRequest(
                                com.android.volley.Request.Method.POST,
                                url,
                                jsonObject,
                                new com.android.volley.Response.Listener<JSONObject>() {
                                    @Override
                                    public void onResponse(JSONObject response) {
                                        Gson gson = new Gson();
                                        Token token = gson.fromJson(response.toString(), Token.class);

                                        SharedPreferences sharedPreferences = getSharedPreferences("StoredValues", MODE_PRIVATE);
                                        SharedPreferences.Editor editor = sharedPreferences.edit();
                                        editor.putString("token", token.toString());
                                        editor.apply();

                                        Intent intent;
                                        intent = MainActivity.getIntentWithNewTask(getApplicationContext());
                                        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
                                        startActivity(intent);
                                        LoginActivity.this.finish();

                                        Log.e("REST Response", response.toString());
                                    }
                                },
                                new com.android.volley.Response.ErrorListener() {
                                    @Override
                                    public void onErrorResponse(VolleyError error) {
                                        Utils utils = new Utils(getApplicationContext());
                                        Log.e("REST Response", error.toString());
                                        if(error.networkResponse.statusCode == 400){
                                            utils.DisplayPopup(view, getResources().getString(R.string.invalid_credentials));
                                        }
                                    }
                                });
                        objectRequest.setRetryPolicy(new RetryPolicy() {
                            @Override
                            public int getCurrentTimeout() {
                                return 10000;
                            }

                            @Override
                            public int getCurrentRetryCount() {
                                return 10000;
                            }

                            @Override
                            public void retry(VolleyError error) throws VolleyError {
                                Log.e("Volley error", error.toString());
                            }
                        });

                        requestQueue.add(objectRequest);

                    } catch (JSONException e){
                        Log.e("JSON Response", e.toString());
                    }
                }
            }
        });
    }
}

MainActivity.java ：

package com.example.music;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;

import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import com.google.android.material.tabs.TabLayout;

import androidx.viewpager.widget.ViewPager;
import androidx.appcompat.app.AppCompatActivity;

import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;

import com.example.music.ui.main.SectionsPagerAdapter;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter(this, getSupportFragmentManager());
        ViewPager viewPager = findViewById(R.id.view_pager);
        viewPager.setAdapter(sectionsPagerAdapter);
        TabLayout tabs = findViewById(R.id.tabs);
        tabs.setupWithViewPager(viewPager);
        FloatingActionButton fab = findViewById(R.id.fab);

        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.logOut:
                SharedPreferences sharedPreferences = getSharedPreferences("StoredValues", MODE_PRIVATE);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("token", "null");
                editor.apply();
                return true;

            default:
                return super.onOptionsItemSelected(item);
        }
    }

    public static Intent getIntent(Context context) {
        return new Intent(context, MainActivity.class);
    }

    public static Intent getIntentWithNewTask(Context context) {
        if(context!=null)
        {

            Intent intent = getIntent(context);

            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

            return intent;
        }
        return null;
    }

}

最低SDK： 21 目标SDK： 29

编辑2：

我现在通过在MainActivity中重写onBackPressed方法来解决这个问题，以“返回”而不是“返回”。如果有人有其他建议，请告诉我。

Answer 1

如果可行，请尝试类似的简单操作，在您的JSON响应中。

 LoginActivity.this.runOnUiThread(new Runnable() {

        @Override
        public void run() {
            Intent intent = new Intent(LoginActivity.this, MainActivity.class);
            startActivity(intent);
            LoginActivity.this.finish();   
        }
    });

Answer 2

您的问题是您的活动没有在执行UI操作的主线程上开始。我添加了一个处理程序来执行此操作，下面是您更新的LoginActivity代码。

我在Handler中创建了一个onCreate的地方，基本上是Main Thread（因为Handler被附加到创建它的线程上）以及何时得到成功的响应，处理程序将得到通知，并且在Handler中，我们将检查活动是否仍然有效（为避免泄漏，因为用户可以杀死该应用程序，并且您的响应随后也会出现）。

public class LoginActivity extends AppCompatActivity {

    private Handler startMainActivityHandler;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        GlobalVariables globalVariables = new GlobalVariables();
        startMainActivityHandler = new StartActivityHandler(this);

        final TextView title = findViewById(R.id.title);
        final EditText email = findViewById(R.id.emailInput);
        final EditText password = findViewById(R.id.passwordInput);
        final Button signUp = findViewById(R.id.signUp);
        Button signIn = findViewById(R.id.signIn);

        //check if token exists
        SharedPreferences sharedPreferences = getSharedPreferences("StoredValues", MODE_PRIVATE);
        String token = sharedPreferences.getString("token", "null");
        if(!token.equals("null")){
            globalVariables.setToken(token);
            Intent myIntent = new Intent(LoginActivity.this, MainActivity.class);
            LoginActivity.this.startActivity(myIntent);
        }

        signUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent openRegisterActivity = new Intent(LoginActivity.this, RegisterActivity.class);

                Pair[] pairs = new Pair[4];
                pairs[0] = new Pair<View, String>(title, "titleTransition");
                pairs[1] = new Pair<View, String>(email, "emailTransition");
                pairs[2] = new Pair<View, String>(password, "passwordTransition");
                pairs[3] = new Pair<View, String>(signUp, "signUpTransition");

                ActivityOptions options = ActivityOptions.makeSceneTransitionAnimation(LoginActivity.this, pairs);
                getWindow().setExitTransition(null);
                startActivity(openRegisterActivity, options.toBundle());
            }
        });

        signIn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(final View view) {
                Utils utils = new Utils(getApplicationContext());
                GlobalVariables globalVariables = new GlobalVariables();
                if(email.getText().toString().equals("") || password.getText().toString().equals("")){
                    //at least one input is empty
                    utils.DisplayPopup(view, getResources().getString(R.string.empty_input_box));
                }
                else{
                    //everything is good to go
                    String url = globalVariables.getIPAddress() + "login/";

                    RequestQueue requestQueue = Volley.newRequestQueue(getApplicationContext());

                    try {
                        JSONObject jsonObject = new JSONObject();
                        jsonObject.put("username", email.getText().toString());
                        jsonObject.put("password", password.getText().toString());

                        JsonObjectRequest objectRequest = new JsonObjectRequest(
                                com.android.volley.Request.Method.POST,
                                url,
                                jsonObject,
                                new com.android.volley.Response.Listener<JSONObject>() {
                                    @Override
                                    public void onResponse(JSONObject response) {
                                        Gson gson = new Gson();
                                        Token token = gson.fromJson(response.toString(), Token.class);

                                        SharedPreferences sharedPreferences = getSharedPreferences("StoredValues", MODE_PRIVATE);
                                        SharedPreferences.Editor editor = sharedPreferences.edit();
                                        editor.putString("token", token.toString());
                                        editor.apply();


                                        Log.e("REST Response", response.toString());
                                        startMainActivityHandler.sendEmptyMessage(1);
                                    }
                                },
                                new com.android.volley.Response.ErrorListener() {
                                    @Override
                                    public void onErrorResponse(VolleyError error) {
                                        Utils utils = new Utils(getApplicationContext());
                                        Log.e("REST Response", error.toString());
                                        if(error.networkResponse.statusCode == 400){
                                            utils.DisplayPopup(view, getResources().getString(R.string.invalid_credentials));
                                        }
                                    }
                                });
                        objectRequest.setRetryPolicy(new RetryPolicy() {
                            @Override
                            public int getCurrentTimeout() {
                                return 10000;
                            }

                            @Override
                            public int getCurrentRetryCount() {
                                return 10000;
                            }

                            @Override
                            public void retry(VolleyError error) throws VolleyError {
                                Log.e("Volley error", error.toString());
                            }
                        });

                        requestQueue.add(objectRequest);

                    } catch (JSONException e){
                        Log.e("JSON Response", e.toString());
                    }
                }
            }
        });
    }

    private static class StartActivityHandler extends Handler {

        private final WeakReference<Activity> weakReference;

        StartActivityHandler(Activity activity) {
            weakReference = new WeakReference<Activity>(activity);
        }

        @Override
        public void handleMessage(@NonNull Message msg) {
            if (msg.what == 1 && weakReference.get() != null && !weakReference.get().isDestroyed()) {
                Intent intent;
                intent = MainActivity.getIntentWithNewTask(getApplicationContext());
                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
                weakReference.get().startActivity(intent);
                weakReference.get().finish();

            }
        }
    }
}

Answer 3

简单地

Intent intent = new Intent(LoginActivity.this, MainActivity.class);
startActivity(intent);
this.finish();

应该工作，如果在您的情况下不工作，那么我建议您创建一个包含2个活动的简单项目，然后尝试一下。或将您现有的项目上传到git，我可以为您提供帮助。

Android Back Stack无法清除

3 个答案: