如何在Android中重定向2个按钮到不同的意图？

Question

在此输入图像说明

我在每个按钮上都安装了一个监听器，这些监听器将我带到不同的活动中。登录按钮工作完美，但注册按钮停止应用程序时，我点击它。

我尝试在_btnreg listener中放入toast消息，结果成功了...

我有一个错误：

package com.example.android.virtualshelter;
import android.content.ContentValues;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.*;   
public class MainActivity extends AppCompatActivity
{
Button _btnreg, _btnlogin;

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

    _btnlogin  = findViewById(R.id.btnlogin);
    _btnreg    = findViewById(R.id.btnreg);

    _btnreg.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            Intent intent = new Intent(MainActivity.this,register.class);
            startActivity(intent);
        }
    });

    _btnlogin.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            Intent intent = new Intent(MainActivity.this,login.class);
            startActivity(intent);
        }
    });
}
}

我的Register.java代码

package com.example.android.virtualshelter;

import android.content.ContentValues;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class register extends AppCompatActivity
{

SQLiteOpenHelper openHelper;
SQLiteDatabase db;
Button _btnReg;
EditText _txtfname, _txtlname, _txtpass, _txtemail, _txtphone;

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

    openHelper = new DatabaseHelper(register.this);
    _txtfname  = findViewById(R.id.txtfname);
    _txtlname  = findViewById(R.id.txtlname);
    _txtpass   = findViewById(R.id.txtpass);
    _txtemail  = findViewById(R.id.txtemail);
    _txtphone  = findViewById(R.id.txtphone);
    _btnReg    = findViewById(R.id.btnreg);

    _btnReg.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            db = openHelper.getWritableDatabase();
            String fname = _txtfname.getText().toString();
            String lname = _txtlname.getText().toString();
            String pass = _txtpass.getText().toString();
            String email = _txtemail.getText().toString();
            String phone = _txtphone.getText().toString();
            insertdata(fname, lname, pass, email, phone);
            Toast.makeText(getApplicationContext(), "register successfully", Toast.LENGTH_LONG).show();

        }
    });
}

public void insertdata(String fname, String lname, String pass, String email, String phone)
{
    ContentValues contentValues = new ContentValues();
    contentValues.put(DatabaseHelper.COL_2, fname);
    contentValues.put(DatabaseHelper.COL_3, lname);
    contentValues.put(DatabaseHelper.COL_4, pass);
    contentValues.put(DatabaseHelper.COL_5, email);
    contentValues.put(DatabaseHelper.COL_6, phone);
    long id = db.insert(DatabaseHelper.TABLE_NAME, null, contentValues);
}
 }

我想转到activity Register.java，但应用程序崩溃了

Answer 1

我的预感是，你找不到按钮，导致一个NPE时设置的列表。可能是您没有在r.layout.activity_main中定义按钮，而是在不同的布局中定义按钮。