Question

我正在尝试将字符串从活动传递到另一个。我经历了许多提到“意图”和“传递字符串”的问题，但我仍然遇到同样的错误。有人能指出我在哪里弄错了吗？这是我的代码

第一项活动

    package com.example.youtube;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.text.Editable;
import android.view.Menu;
import android.widget.EditText;
import android.widget.TextView;

public class Testing extends Activity {

    public static String IPAddress = "";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_testing);


        //Alert Popup
        AlertDialog.Builder alert = new AlertDialog.Builder(this);

        alert.setTitle("Step 1");
        alert.setMessage("Enter IP Address\n(i.e: 192.168.0.1)");       


        // Set an EditText view to get user input 
        final EditText input = new EditText(this);
        alert.setView(input);

        alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
          Editable value = input.getText();
          // Do something with value!
          IPAddress = value.toString();

            //Fire that second activity
            Intent intent = new Intent( getBaseContext(),LoginIn.class);
            intent.putExtra("keyword1",IPAddress);  
            startActivity( intent);

            if (IPAddress != ""){

                startActivity(new Intent("com.example.youtube.LoginIn"));
            }
          }
        });



        alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int whichButton) {
            // Canceled.
            finish();
            System.exit(0);
          }
        });

        alert.show();



    }

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
    }

    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        finish();
        System.exit(0);
    }


}

第二项活动

    package com.example.youtube;

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


public class LoginIn extends Activity {

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

        Button bverify = (Button) findViewById(R.id.verify1);
        final TextView testview = (TextView) findViewById(R.id.textView3);

        Bundle extras=getIntent().getExtras();
        String value1=extras.getString("keyword1");

        bverify.setOnClickListener(new View.OnClickListener() 
        {

            public void onClick(View v) {
                // TODO Auto-generated method stub
                startActivity(new Intent("com.example.youtube.domotique"));
            }
        });




    }

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
    }

    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        finish();
        System.exit(0);
    }

}

清单

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.youtube"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

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

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


        <activity
            android:name=".LoginIn"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="com.example.youtube.LoginIn" />

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

        <activity
            android:name=".domotique"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="com.example.youtube.domotique" />

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

    </application>

</manifest>

logcat的

    threadid=1: thread exiting with uncaught exception (group=0x40020ac0)
FATAL EXCEPTION: main
Unable to start activity ComponentInfo{com.example.youtube/com.example.youtube.LoginIn}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
at android.app.ActivityThread.access$2300(ActivityThread.java:125)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.youtube.LoginIn.onCreate(LoginIn.java:23)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)

我尝试了许多形式的Intent，并且在我的代码中的不同位置，但是当我的第二个活动启动时，我的应用程序在按“Ok”时仍然崩溃。

感谢您的帮助!!

Answer 1

在第一个活动中评论此部分并执行代码，如果您遇到相同的错误，则可能未在清单中注册“com.example.youtube.domotique”和“com.example.youtube.LoginIn” / p>

if (IPAddress != ""){

                    startActivity(new Intent("com.example.youtube.LoginIn"));
                }

传递字符串错误

1 个答案: