android-studio - android数据传值再获取的问题

Question

初学，这段代码也是在网上找的

开发选用的SDK是4.0,ADT是5.0，测试手机是4.4.4

在Layout_1中的传递代码

Intent intentSimple = new Intent();
intentSimple.setClass(Layout_1.this,Layout_2.class);

Bundle bundleSimple = new Bundle();
bundleSimple.putString("username", username);
bundleSimple.putString("password",password);
intentSimple.putExtras(bundleSimple);
startActivity(intentSimple);

在Layout_2中的获取代码

   Bundle bundle = this.getIntent().getExtras();
   username = bundle.getString("username");
   password = bundle.getString("password");

运行会出现这个错误提示“ java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference”

运行会出现一个错误提示“很抱歉，XXX已停止运行”，虽然出现这个错误提示，点击“确定”之后程序会继续运行，变量数据也能获取到

请问如何处理?

全部代码如下

Layout_1

package com.hl;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.TextView;
import android.widget.Toast;

public class Layout_1 extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.layout_1);


        findViewById(R.id.login).setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                TextView usernameView = (TextView) findViewById(R.id.username);
                String username = usernameView.getText().toString().trim();
                TextView passwordView = (TextView) findViewById(R.id.password);
                String password = passwordView.getText().toString().trim();

                Intent intentSimple = new Intent();
                intentSimple.setClass(Layout_1.this,Layout_2.class);

                Bundle bundleSimple = new Bundle();
                bundleSimple.putString("username", username);
                bundleSimple.putString("password",password);
                intentSimple.putExtras(bundleSimple);
                startActivity(intentSimple);


                Intent intent1 = new Intent(Layout_1.this, Layout_2.class);
                startActivity(intent1);

            }
        });

        }


}

Layout_2

package com.hl;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.widget.Toast;


public class Layout_2 extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.layout_2);

        Bundle bundle = this.getIntent().getExtras();
        String username = bundle.getString("username");
        String password = bundle.getString("password");
        Toast.makeText(Layout_2.this, username + "  " + password, Toast.LENGTH_SHORT).show();

    }

}

Answer 1

你上面的程式碼是沒問題的，所以你確定你的username與password賦了值？
如果賦了值那就不是這裡的問題了 你把程式碼都貼出來吧。

Answer 2

startactivity函數呼叫了兩次，第一次呼叫時有值傳遞，第二次傳遞沒有值
Intent intentSimple = new Intent();
intentSimple.setClass(Layout_1.this,Layout_2.class);

Bundle bundleSimple = new Bundle();
bundleSimple.putString("username", username);
bundleSimple.putString("password",password);
intentSimple.putExtras(bundleSimple); Intent intent1 = new Intent(Layout_1.this, Layout_2.class);
startActivity(intent1);

Answer 3

從程式碼看是layout_2裡的bundle為null導致的，要看你這段程式碼是在哪裡執行的，可能當時沒有拿到bundle資料呢