Question

我正在尝试登录并注册应用程序，其中寄存器详细信息存储在android studio中的数据库中。你可以帮助我，因为当我运行我的程序时，下一页不会出现（显示一个页面的代码，它不会出现在主菜单中，这是注册活动）。如果你也知道如何为登录做一个sql数据库并在android studio中注册将非常感激。感谢

主要活动：

package com.example.emily.loginapp;

import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    Button Login, Register, Delete, Update;
    int status = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Login = (Button) findViewById(R.id.Login);
        Register = (Button) findViewById(R.id.Register);
        Delete = (Button) findViewById(R.id.Delete);
        Update = (Button) findViewById(R.id.Update);
        Login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                status = 1;
                Bundle b = new Bundle();
                b.putInt("status", status);
                Intent i = new Intent("login_filter");
                i.putExtras(b);
                startActivity(i);
            }

        });
        Register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent("register_filter");
                startActivity(i);
            }
        });
        Update.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                status = 2;
                Bundle b = new Bundle();
                b.putInt("status", status);
                Intent i = new Intent("login_filter");
                i.putExtras(b);
                startActivity(i);
            }
        });
        Delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
        status= 3;
                Bundle b = new Bundle();
                b.putInt("status", status);
                Intent i = new Intent("login_filter");
                i.putExtras(b);
                startActivity(i);

            }
        });
    }
}

寄存器：

package com.example.emily.loginapp;                                                                                  

import android.content.Context;                                                                                      
import android.support.v7.app.AppCompatActivity;                                                                     
import android.view.View;                                                                                            
import android.os.Bundle;                                                                                            
import android.widget.EditText;                                                                                      
import android.widget.Button;                                                                                        
import android.widget.Toast;                                                                                         


public class RegisterActivity extends AppCompatActivity {                                                            

     EditText USER_NAME, USER_PASS, CON_PASS;                                                                        
    String user_name, user_pass,con_pass;                                                                            
Button REG;                                                                                                          
    Context ctx = this;                                                                                              

    @Override                                                                                                        
    protected void onCreate(Bundle savedInstanceState) {                                                             
        super.onCreate(savedInstanceState);                                                                          
        setContentView(R.layout.content_register);                                                                   

    USER_NAME = (EditText) findViewById(R.id.reg_user);                                                              
        USER_PASS = (EditText)findViewById(R.id.reg_pass);                                                           
        CON_PASS = (EditText) findViewById(R.id.con_pass);                                                           
REG = (Button) findViewById(R.id.user_reg);                                                                          
        REG.setOnClickListener(new View.OnClickListener() {                                                          
            @Override                                                                                                
            public void onClick(View v) {                                                                            
                user_name = USER_NAME.getText().toString();                                                          
                user_pass = USER_PASS.getText().toString();                                                          
                con_pass = CON_PASS.getText().toString();                                                            

                if (!(user_pass.equals(con_pass))){                                                                  
                    Toast.makeText(getBaseContext(),"Passwords are not matching", Toast.LENGTH_LONG).show();;        
                USER_NAME.setText("");                                                                               
                    USER_PASS.setText("");                                                                           
                    CON_PASS.setText("");                                                                            
                }else{                                                                                               
                    DatabaseOperations DB = new DatabaseOperations(ctx);                                             
                    DB.putInformation(DB, user_name, user_pass);                                                     
                    Toast.makeText(getBaseContext(),"Registration success", Toast.LENGTH_LONG).show();               
                    finish();                                                                                        

                }                                                                                                    
            }                                                                                                        
        });                                                                                                          

    }                                                                                                                

}

LOGCAT:
03-09 22:33:25.504 2672-2672/com.example.emily.loginapp D/AndroidRuntime: Shutting down VM
03-09 22:33:25.537 2672-2672/com.example.emily.loginapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.emily.loginapp, PID: 2672
    android.content.ActivityNotFoundException: No Activity found to handle Intent { act=register_filter }
      at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1798)
      at android.app.Instrumentation.execStartActivity(Instrumentation.java:1512)
      at android.app.Activity.startActivityForResult(Activity.java:3917)
      at android.app.Activity.startActivityForResult(Activity.java:3877)
      at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:784)
      at android.app.Activity.startActivity(Activity.java:4200)
      at android.app.Activity.startActivity(Activity.java:4168)
      at com.example.emily.loginapp.MainActivity$2.onClick(MainActivity.java:43)
      at android.view.View.performClick(View.java:5198)
      at android.view.View$PerformClick.run(View.java:21147)
      at android.os.Handler.handleCallback(Handler.java:739)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:148)
      at android.app.ActivityThread.main(ActivityThread.java:5417)
      at java.lang.reflect.Method.invoke(Native Method)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
03-09 22:33:36.952 2672-2679/com.example.emily.loginapp W/art: Suspending all threads took: 29.841ms

清单：

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".DeleteActivity"
            android:label="@string/title_activity_delete"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".LoginActivity"
            android:label="@string/title_activity_login"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".RegisterActivity"
            android:label="@string/title_activity_register"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".UpdateActivity"
            android:label="@string/title_activity_update"
            android:theme="@style/AppTheme.NoActionBar"></activity>
    </application>

</manifest>

Answer 1

您需要使用intent扩展class来创建Activity。例如：

Intent i = new Intent(this, SomeActivity.class);
startActivity(i);

其中this是当前Context，而SomeActivity是您要开始的活动。

看看文档：

http://developer.android.com/training/basics/firstapp/starting-activity.html

Answer 2

您正在使用设备上没有的意图标记（ register_filter ），这就是崩溃应用程序的原因......！

应该使用上下文调用Intent类的构造函数活动/应用程序和您必须移动的活动（如果您是不使用设备上没有的活动）......！

您应该使用以下代码访问RegisterActivity，

Intent i = new Intent(MainActivity.this, RegistrationActivity.class);
startActivity(i);

Answer 3

要从当前活动中调用新活动，您需要传递当前活动的上下文和＆＃34; NewClass＆＃34;你想打开它作为参数。

例如：

    Intent i = new Intent(CurrentClassName.this, TheClassToBeOpened.class);
    startActivity(i);

Answer 4

恕我直言，使用行动对你想要达到的目标来说是过度的。你应该只是这样的东西：

Intent i = new Intent(getContext(), RegistrationActivity.class);
startActivity(i);

（您也可以使用this代替getContext()。）

如果您确实确实想要使用actions，那么您必须在活动中定义意图过滤器register_filter。一些事情：

<activity
    android:name=".LoginActivity"
    android:label="@string/title_activity_login"
    android:theme="@style/AppTheme.NoActionBar">
    <intent-filter>
        <action android:name="login_filter" />
    </intent-filter> 
</activity>

应该这样做。

如需参考，请查看documentation和this question。

为什么我的程序在单击按钮时崩溃了？

4 个答案: