不幸的是，appname已停止

-1

我正試圖做一個簡單的android程序，啓動mainActivity，當用戶點擊按鈕secondActivity打開並顯示一個收音機組與三個單選按鈕。當用戶點擊單選按鈕並按下按鈕時，該字符串傳遞給mainActivity並應顯示在textView On mainActivity上。但是，當我按主要活動打開SecondActivity按鈕。錯誤消息顯示不幸的是，radioButtons已停止。我已經更新了清單還..不幸的是，appname已停止

這裏是我的代碼：

mainActivity.java

package com.example.radiobuttons; 

import android.support.v4.widget.SimpleCursorAdapter.ViewBinder; 
import android.support.v7.app.ActionBarActivity; 
import android.app.Activity; 
import android.content.Intent; 
import android.os.Bundle; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.widget.Button; 
import android.widget.TextView; 
import android.view.View; 


public class MainActivity extends Activity { 

    TextView txt1; 
    Button b1; 
    int requestCode = 12; 

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

     Link(); 
     b1.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 
       // TODO Auto-generated method stub 
       Intent in = new Intent(MainActivity.this , secondActivity.class); 
       startActivityForResult(in, requestCode); 
      } 
     }); 

    } 

    public void Link() 
    { 
     txt1 = (TextView) findViewById(R.id.txtView1); 
     b1 = (Button) findViewById(R.id.Button1); 
    } 



    @Override 
    protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
     // TODO Auto-generated method stub 
     super.onActivityResult(requestCode, resultCode, data); 
     if (resultCode == 110){ 
     String txt = "Your Answer Is " +data.getStringExtra("answer"); 

     } 

    } 





}

secondActivity.java

package com.example.radiobuttons; 

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

public class secondActivity extends Activity { 

    RadioGroup rg; 
    Button b1; 
    String ans; 
    Intent in; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.second); 
     Link(); 

     rg.setOnCheckedChangeListener(new OnCheckedChangeListener() { 

      @Override 
      public void onCheckedChanged(RadioGroup group, int checkedId) { 
       // TODO Auto-generated method stub 

       switch (group.getId()) 
       { 
       case R.id.radio0: 
        ans = "Manmohan Singh"; 

        break; 
       case R.id.radio1: 
        ans = "Mulayam Singh"; 
        break; 
       case R.id.radio2: 
        ans = "Narender Modi"; 
        break; 
       } 

      } 
     }); 

     b1.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 
       // TODO Auto-generated method stub 
       in = new Intent(); 
       in.putExtra("answer", ans); 
       setResult(110,in); 
       finish(); 
      } 
     }); 
    } 

    public void Link() 
    { 
     rg = (RadioGroup) findViewById(R.id.radioGroup1); 
     b1 = (Button) findViewById(R.id.Button1); 

    } 
}

單選按鈕清單

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

    <uses-sdk 
     android:minSdkVersion="8" 
     android:targetSdkVersion="21" /> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/AppTheme" > 
     <activity 
      android:name=".MainActivity" 
      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=".secondActivity" 
      android:label="@string/app_name" > 
      <intent-filter> 
       <action android:name="com.example.radiobutton.SECONDACTIVITY" /> 

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

</manifest>

LogCat：

06-20 12:44:05.319: E/AndroidRuntime(1905): FATAL EXCEPTION: main 
06-20 12:44:05.319: E/AndroidRuntime(1905): Process: com.example.radiobuttons, PID: 1905 
06-20 12:44:05.319: E/AndroidRuntime(1905): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.radiobuttons/com.example.radiobuttons.secondActivity}: java.lang.NullPointerException 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.ActivityThread.access$800(ActivityThread.java:135) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.os.Handler.dispatchMessage(Handler.java:102) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.os.Looper.loop(Looper.java:136) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.ActivityThread.main(ActivityThread.java:5001) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at java.lang.reflect.Method.invokeNative(Native Method) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at java.lang.reflect.Method.invoke(Method.java:515) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at dalvik.system.NativeStart.main(Native Method) 
06-20 12:44:05.319: E/AndroidRuntime(1905): Caused by: java.lang.NullPointerException 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at com.example.radiobuttons.secondActivity.onCreate(secondActivity.java:47) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.Activity.performCreate(Activity.java:5231) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148) 
06-20 12:44:05.319: E/AndroidRuntime(1905):  ... 11 more

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context="com.example.radiobuttons.MainActivity" > 

    <TextView 
     android:id="@+id/txtView1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/hello_world" /> 
    <Button 
     android:id="@+id/Button1" 
     android:layout_height="wrap_content" 
     android:layout_width="fill_parent" 
     android:gravity="center_horizontal" 
     android:layout_below="@+id/txtView1" 
     android:text="Get Input From Second Activity" /> 

</RelativeLayout>

second.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" > 

    <TextView 
     android:id="@+id/textView1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/radioGroup1" 
     android:layout_alignParentTop="true" 
     android:layout_marginTop="17dp" 
     android:text="Prime Minister Of India?" /> 

    <RadioGroup 
     android:id="@+id/radioGroup1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_below="@+id/textView1" 
     android:layout_marginLeft="30dp" 
     android:layout_marginTop="21dp" > 

     <RadioButton 
      android:id="@+id/radio0" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 

      android:text="Manmohan Singh" /> 

     <RadioButton 
      android:id="@+id/radio1" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="Mulayam Singh" /> 

     <RadioButton 
      android:id="@+id/radio2" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="Narender Modi" /> 
    </RadioGroup> 

    <Button 
     android:id="@+id/button1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/radioGroup1" 
     android:layout_below="@+id/radioGroup1" 
     android:layout_marginTop="39dp" 
     android:text="Submit Answer" /> 

</RelativeLayout>

來源

2015-06-20 Akshay

請同時附上各自的xmls – Droidekas

我已經在Link（）中初始化了b1; – Akshay

是的，但xmls也將幫助。請將它們添加，這將完成您的問題 – Droidekas

你null pointer exception因爲您設置了錯誤的ID。在你的xml中你給出了android:id="@+id/button1"，但是你在Link（）中使用了Button1。

來源

2015-06-20 17:05:45 Pooja

在你Link()方法改變按鈕初始化：

b1 = (Button) findViewById(R.id.button1);

來源

2015-06-20 17:02:16 mattfred

不幸的是，appname已停止

回答

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