Android-Nullzeiger-Ausnahme bei view.getId()

-1

Dieser Code gibt eine Nullzeiger-Ausnahme in der onClick() -Methode an. Ich habe andere Beiträge überprüft, aber keine richtigen Lösungen gefunden. Bitte helfen Sie. Das ist mein erstes Android-Projekt und ich kann es nicht lösen. Wo ist der Fehler dabei? Dies scheint der Weg zu sein, die ich in anderen LösungenAndroid-Nullzeiger-Ausnahme bei view.getId()

public class MainActivity extends Activity implements OnClickListener{ 

     Button btn0,btn1,btn2,btn3,btn4,btn5,btn6,btn7,btn8,btn9,btnAdd,btnSub,btnDiv,btnMul,btnDot,btnSign,btnAns,btnCE,btnC,btnDel; 
     EditText et; 
     char last; 
     double num,num1,num2; 
     boolean signFlag,numFlag; 

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

      //Initializing variables 
      btn0=(Button) findViewById(R.id.btn0); 
      btn1=(Button) findViewById(R.id.btn1); 
      btn2=(Button) findViewById(R.id.btn2); 
      btn3=(Button) findViewById(R.id.btn3); 
      btn4=(Button) findViewById(R.id.btn4); 
      btn5=(Button) findViewById(R.id.btn5); 
      btn6=(Button) findViewById(R.id.btn6); 
      btn7=(Button) findViewById(R.id.btn7); 
      btn8=(Button) findViewById(R.id.btn8); 
      btn9=(Button) findViewById(R.id.btn9); 
      btnAdd=(Button) findViewById(R.id.btnAdd); 
      btnSub=(Button) findViewById(R.id.btnSub); 
      btnMul=(Button) findViewById(R.id.btnMul); 
      btnDiv=(Button) findViewById(R.id.btnDiv); 
      btnDot=(Button) findViewById(R.id.btnDot); 
      btnSign=(Button) findViewById(R.id.btnSign); 
      btnAns=(Button) findViewById(R.id.btnAns); 
      btnCE=(Button) findViewById(R.id.btnCE); 
      btnC=(Button) findViewById(R.id.btnC); 
      btnDel=(Button) findViewById(R.id.btnDel); 
      num1=0; num2=0; num=0; 
      signFlag=false; numFlag=false; 
      //Initializing variables ends here 

      //Setting onClickListner 
      btn0.setOnClickListener(this); 
      btn1.setOnClickListener(this); 
      btn2.setOnClickListener(this); 
      btn3.setOnClickListener(this); 
      btn4.setOnClickListener(this); 
      btn5.setOnClickListener(this); 
      btn6.setOnClickListener(this); 
      btn7.setOnClickListener(this); 
      btn8.setOnClickListener(this); 
      btn9.setOnClickListener(this); 
      btnAdd.setOnClickListener(this); 
      btnDiv.setOnClickListener(this); 
      btnSub.setOnClickListener(this); 
      btnMul.setOnClickListener(this); 
      btnSign.setOnClickListener(this); 
      btnAns.setOnClickListener(this); 
      btnDot.setOnClickListener(this); 
      btnCE.setOnClickListener(this); 
      btnC.setOnClickListener(this); 
      btnDel.setOnClickListener(this); 
      //Setting onClickListner Ends here 
     } 

     @Override 
     public boolean onCreateOptionsMenu(Menu menu) { 
      // Inflate the menu; this adds items to the action bar if it is present. 
      getMenuInflater().inflate(R.menu.main, menu); 
      return true; 
     } 

     @Override 
     public boolean onOptionsItemSelected(MenuItem item) { 
      // Handle action bar item clicks here. The action bar will 
      // automatically handle clicks on the Home/Up button, so long 
      // as you specify a parent activity in AndroidManifest.xml. 
      int id = item.getItemId(); 
      if (id == R.id.action_settings) { 
       return true; 
      } 
      return super.onOptionsItemSelected(item); 
     } 

     @Override 
     public void onClick(View v) { 
      // TODO Auto-generated method stub 

      int id =v.getId(); //NullPointerException somewhere around here 
      switch (id) { 
      case R.id.btn0: 
       printNum('0'); 
       break; 
      case R.id.btn1: 
       printNum('1'); 
       break; 
      case R.id.btn2: 
       printNum('2'); 
       break; 
      case R.id.btn3: 
       printNum('3'); 
       break; 
      case R.id.btn4: 
       printNum('4'); 
       break; 
      case R.id.btn5: 
       printNum('5'); 
       break; 
      case R.id.btn6: 
       printNum('6'); 
       break; 
      case R.id.btn7: 
       printNum('7'); 
       break; 
      case R.id.btn8: 
       printNum('8'); 
       break; 
      case R.id.btn9: 
       printNum('9'); 
       break; 
      case R.id.btnAdd: 
       num=Integer.parseInt(et.getText().toString())+num; 
       et.setText(""); 
       signFlag=true; 
       last='+'; 
       break; 
      case R.id.btnSub: 
       num=Integer.parseInt(et.getText().toString())-num; 
       et.setText(""); 
       signFlag=true; 
       last='-'; 
       break;  
      case R.id.btnMul: 
       if(signFlag==false) 
        num=Integer.parseInt(et.getText().toString()); 
       else 
        num=Integer.parseInt(et.getText().toString())*num; 
       et.setText(""); 
       signFlag=true; 
       last='*'; 
       break;  
      case R.id.btnDiv: 
       if(signFlag==false) 
        num=Integer.parseInt(et.getText().toString()); 
       else 
        num=Integer.parseInt(et.getText().toString())/num; 
       et.setText(""); 
       signFlag=true; 
       last='/'; 
       break;  
      case R.id.btnDot: 
       et.setText(et.getText().toString()+"."); 
       break;  
      case R.id.btnSign: 
       double temp=Integer.parseInt(et.getText().toString()); 
       temp=temp*(-1); 
       et.setText(temp+""); 
       break; 
      case R.id.btnAns: 

       break; 
      default: 
       break; 
      } 
     } 

     public void printNum(char c) { 
      String temp=""; 
      if(numFlag){ 
       temp=et.getText().toString(); 
      } 
      temp+=c; 
      Dialog dialog = new Dialog(this); 
      dialog.show(); 

      et.setText(temp); 
     } 

    }

Die Layout-Datei gesehen haben:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:id="@+id/LinearLayout2" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" 
    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.calculator.MainActivity" > 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 

     <EditText 
      android:id="@+id/ET" 
      android:layout_width="0dp" 
      android:layout_height="wrap_content" 
      android:layout_weight="1" 
      android:ems="10" 
      android:inputType="numberDecimal" /> 

    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnCE" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="CE" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnC" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="C" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnDel" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="DEL" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnDiv" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="/" /> 
    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn7" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="7" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn8" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="8" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn9" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="9" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnMul" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="*" /> 
    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn4" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="4" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn5" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="5" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn6" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="6" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnSub" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="-" /> 
    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn1" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="1" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn2" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="2" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn3" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="3" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnAdd" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="+" /> 
    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" > 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnSign" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="+-" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btn0" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="0" /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnDot" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="." /> 

     <Button style="?android:attr/buttonBarButtonStyle" 
      android:id="@+id/btnAns" 
      android:layout_width="70dp" 
      android:layout_height="70dp" 
      android:text="=" /> 

    </LinearLayout> 

</LinearLayout>

Die logcat:

07-18 08:12:03.890: D/gralloc_goldfish(962): Emulator without GPU emulation detected. 
07-18 08:12:06.580: D/AndroidRuntime(962): Shutting down VM 
07-18 08:12:06.580: W/dalvikvm(962): threadid=1: thread exiting with uncaught exception (group=0xb4ab0ba8) 
07-18 08:12:06.580: E/AndroidRuntime(962): FATAL EXCEPTION: main 
07-18 08:12:06.580: E/AndroidRuntime(962): Process: com.example.calculator, PID: 962 
07-18 08:12:06.580: E/AndroidRuntime(962): java.lang.NullPointerException 
07-18 08:12:06.580: E/AndroidRuntime(962): at com.example.calculator.MainActivity.printNum(MainActivity.java:187) 
07-18 08:12:06.580: E/AndroidRuntime(962): at com.example.calculator.MainActivity.onClick(MainActivity.java:103) 
07-18 08:12:06.580: E/AndroidRuntime(962): at android.view.View.performClick(View.java:4438) 
07-18 08:12:06.580: E/AndroidRuntime(962): at android.view.View$PerformClick.run(View.java:18422) 
07-18 08:12:06.580: E/AndroidRuntime(962): at android.os.Handler.handleCallback(Handler.java:733) 
07-18 08:12:06.580: E/AndroidRuntime(962): at android.os.Handler.dispatchMessage(Handler.java:95) 
07-18 08:12:06.580: E/AndroidRuntime(962): at android.os.Looper.loop(Looper.java:136) 
07-18 08:12:06.580: E/AndroidRuntime(962): at android.app.ActivityThread.main(ActivityThread.java:5001) 
07-18 08:12:06.580: E/AndroidRuntime(962): at java.lang.reflect.Method.invokeNative(Native Method) 
07-18 08:12:06.580: E/AndroidRuntime(962): at java.lang.reflect.Method.invoke(Method.java:515) 
07-18 08:12:06.580: E/AndroidRuntime(962): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
07-18 08:12:06.580: E/AndroidRuntime(962): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
07-18 08:12:06.580: E/AndroidRuntime(962): at dalvik.system.NativeStart.main(Native Method) 
07-18 08:12:09.940: I/Process(962): Sending signal. PID: 962 SIG: 9

Quelle

2016-07-18 Kishan Shah

Zeigen Sie Ihre Logcat Ausgabe schreiben. –

Stapelverfolgung? Layoutdatei, zeigen Sie uns, was Sie haben, macht es viel einfacher zu helfen – finki

Wo initialisieren Sie 'et' Variable? –

Sie diese beiden fehlen könnte:

Verwenden Sie anstelle von switch(id) diese

public void clicker(View v) { 
     switch (v.getId()) { 
      case R.id.btnmhome: 
       cf.gohome(); 
       break; 
      } 
     }

Und schreiben

android:onClick="clicker"

es Ihre Methode Name bedeutet, wo Sie onclick funtion

Quelle

2016-07-18 12:12:20 Punithapriya

Früher war es switch (v.getId()), aber dann habe ich irgendwo gefunden int int = v.getId() also habe ich es versucht. Und es gibt mehrere Schaltflächen, also habe ich einen Listener implementiert, anstatt die onClick-Eigenschaft in xml zu ändern. –

Sie haben Ihre Edittext-ID vergessen, um sie in oncreate zu definieren. –

Sie sehen, dass Sie die Textvariable nicht initialisiert haben. Machen Sie die Deklaration für editierte Texte wie andere Ansichten. – Punithapriya

Android-Nullzeiger-Ausnahme bei view.getId()

Antwort

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