android.content.Context.getPackageName（）'null对象引用

-1

我在android中遇到问题并且出现问题上面的错误显示了我尝试从登录按钮登录活动时打开主要活动。android.content.Context.getPackageName（）'null对象引用

当按下登录按钮突然应用程式停止和下面的错误被表示

以下错误是表示机器人监视器

10-20 18:47:23.314 13432-13432/com.antherx.prasenjit.ihdfbachatgat E/AndroidRuntime: FATAL EXCEPTION: main 
Process: com.antherx.prasenjit.ihdfbachatgat, PID: 13432 
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.antherx.prasenjit.ihdfbachatgat/com.antherx.prasenjit.ihdfbachatgat.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2460) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2629) 
    at android.app.ActivityThread.access$800(ActivityThread.java:182) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1474) 
    at android.os.Handler.dispatchMessage(Handler.java:111) 
    at android.os.Looper.loop(Looper.java:194) 
    at android.app.ActivityThread.main(ActivityThread.java:5706) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1033) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:828) 
    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference 
    at android.content.ContextWrapper.getPackageName(ContextWrapper.java:132) 
    at android.content.ComponentName.<init>(ComponentName.java:77) 
    at android.content.Intent.<init>(Intent.java:4358) 
    at com.antherx.prasenjit.ihdfbachatgat.MainActivity.<init>(MainActivity.java:26) 
    at java.lang.reflect.Constructor.newInstance(Native Method) 
    at java.lang.Class.newInstance(Class.java:1606) 
    at android.app.Instrumentation.newActivity(Instrumentation.java:1071) 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2437) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2629) 
    at android.app.ActivityThread.access$800(ActivityThread.java:182) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1474) 
    at android.os.Handler.dispatchMessage(Handler.java:111) 
    at android.os.Looper.loop(Looper.java:194) 
    at android.app.ActivityThread.main(ActivityThread.java:5706) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1033) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:828)

这登录活动代码是在此代码的任何问题

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_login); 
    //Please do not 

    Email = (EditText)findViewById(R.id.email); 
    Password = (EditText)findViewById(R.id.password); 
    String wel_on_login = "Welcome On IHDF Bachat Gat app"; 
    Toast welcome = Toast.makeText(getApplicationContext(),wel_on_login,Toast.LENGTH_LONG); 
    welcome.show(); 

    final Button signIn = (Button)findViewById(R.id.email_sign_in_button); 
    final Button register = (Button)findViewById(R.id.registration) ; 
    final Intent main_trans = new Intent(this, MainActivity.class); 
    final Intent reg_trans = new Intent(this, register.class); 

    signIn.setOnClickListener(new View.OnClickListener(){ 
     @Override 
     public void onClick(View view) { 

      startActivity(main_trans); 
     } 
    }); 

    register.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      startActivity(reg_trans); 
     } 
    });

这是主要活动代码是他们在这里的任何问题

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

    toolbar = (Toolbar)findViewById(R.id.home_toolbar); 
    setSupportActionBar(toolbar); 
    newMember = (MenuItem)findViewById(R.id.new_member); 
    newProfile = (MenuItem)findViewById(R.id.profile) ; 

    Drawer =(DrawerLayout)findViewById(R.id.drawerLayout); 
    sToggle = new ActionBarDrawerToggle(this,Drawer,R.string.open,R.string.close); 


    Grp_ico = (ImageView)findViewById(R.id.grp_ico); 

    Drawer.addDrawerListener(sToggle); 
    sToggle.syncState(); 

    getSupportActionBar(); 


    String wel_on_main = "You are successfully on Main Home"; 
    Toast welcome = Toast.makeText(getApplicationContext(),wel_on_main,Toast.LENGTH_LONG); 
    welcome.show(); 




} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 

    switch (item.getItemId()){ 

     case R.id.new_member : 
      startActivity(new_new_member); 
     case R.id.profile : 
      startActivity(new_new_profile); 
     case R.id.setting : 
      startActivity(new_new_setting); 
     case R.id.meeting : 
      startActivity(new_new_meeting); 
      default: 
       return super.onOptionsItemSelected(item); 


    } 

}

来源

2016-10-20 Prasenjit Hiwale

另一个过早上下文用法......显然，你不能使用字段初始 – Selvin

环境中的所有代码粘贴MainActivity.class，或者是加26行？ – walkmn

-1

更改getApplicationContext()从

Toast welcome = Toast.makeText(getApplicationContext(),wel_on_main,Toast.LENGTH_LONG);

要么getBaseContext()或最好this

来源

2016-10-21 01:14:03

'... MainActivity。（MainActivity.java:26）'显然这不是问题 – Selvin

@Selvin我看到了，谢谢你的指导 –

他在MainAcitivty类中有一些像'Intent intent = new Intent（this，Some.class）'这样的字段。 ..''表示字段初始值设定项 – Selvin

我，我试图用与意外没有基本上下文的应用程序。

，所以我不得不在我的应用程序重写：

@Override 
    protected void attachBaseContext(Context newBase) { 
} 

//instead of calling its super: 

@Override 
    protected void attachBaseContext(Context newBase) { 
     super.attachBaseContext(newBase);}

来源

2017-06-27 05:04:08 j2emanue

android.content.Context.getPackageName（）'null对象引用

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