ADT簡單應用程序 - 致命異常

-4

我剛剛開始使用Android和Java，並且我剛剛製作了一個帶有幾個文字瀏覽，按鈕和edittext的簡單應用程序。ADT簡單應用程序 - 致命異常

當我運行應用程序時，出現錯誤消息：不幸的是，FirstApp已停止。我熟悉編程，並想知道如果我錯過了一些庫，或者ADT配置錯誤。

我試圖清理並重新生成，要在Package explorer和Android Tools - >添加支持庫中右鍵單擊項目，重新啓動模擬器，重新啓動ADT並重新啓動計算機。不能弄清楚這是什麼。

您可以在這裏看到什麼錯嗎？

MainActivity.java進口

import android.support.v7.app.ActionBarActivity; 
import android.support.v7.app.ActionBar; 
import android.support.v4.app.Fragment; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.*; 
import android.os.Build;

MainActivity.java

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


    Button btnCalc = (Button)findViewById(R.id.btnCalc); 

    btnCalc.setOnClickListener(new View.OnClickListener() { 
     public void onClick(View v) { 
      EditText number = (EditText)findViewById(R.id.num); 
      TextView display = (TextView)findViewById(R.id.display); 

      double num = Double.parseDouble(number.getText().toString()); 
      num = num * 5; 
      display.setText(num + ""); 
     } 
    }); 




    if (savedInstanceState == null) { 
     getSupportFragmentManager().beginTransaction() 
       .add(R.id.container, new PlaceholderFragment()) 
       .commit(); 
    } 
} 


@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; 
}

fragment_main.xml

<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.danlevi.testproject.MainActivity$PlaceholderFragment" > 

<TextView 
    android:id="@+id/title" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignParentTop="true" 
    android:layout_centerHorizontal="true" 
    android:text="@string/lblTitle" /> 

<EditText 
    android:id="@+id/num" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@+id/textView1" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="15dp" 
    android:ems="10" 
    android:inputType="numberDecimal|numberSigned" > 

    <requestFocus /> 
</EditText> 

<Button 
    android:id="@+id/btnCalc" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@+id/num" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="14dp" 
    android:text="@string/btnCalc" /> 

<TextView 
    android:id="@+id/display" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignParentLeft="true" 
    android:layout_below="@+id/btnCalc" 
    android:layout_marginTop="16dp" /> 

</RelativeLayout>

控制檯

[2014-05-16 18:33:16 - TestProject] Dx 
trouble writing output: already prepared 
[2014-05-16 18:33:17 - TestProject] ------------------------------ 
[2014-05-16 18:33:17 - TestProject] Android Launch! 
[2014-05-16 18:33:17 - TestProject] adb is running normally. 
[2014-05-16 18:33:17 - TestProject] Performing com.danlevi.testproject.MainActivity activity launch 
[2014-05-16 18:33:17 - TestProject] Automatic Target Mode: using existing emulator 'emulator-5554' running compatible AVD 'Android' 
[2014-05-16 18:33:17 - TestProject] Uploading TestProject.apk onto device 'emulator-5554' 
[2014-05-16 18:33:18 - TestProject] Installing TestProject.apk... 
[2014-05-16 18:33:30 - TestProject] Success! 
[2014-05-16 18:33:30 - TestProject] Starting activity com.danlevi.testproject.MainActivity on device emulator-5554 
[2014-05-16 18:33:33 - TestProject] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.danlevi.testproject/.MainActivity }

logcat的

05-16 12:33:37.412: D/AndroidRuntime(1579): Shutting down VM 
05-16 12:33:37.412: W/dalvikvm(1579): threadid=1: thread exiting with uncaught exception (group=0xb2b08ba8) 
05-16 12:33:37.432: E/AndroidRuntime(1579): FATAL EXCEPTION: main 
05-16 12:33:37.432: E/AndroidRuntime(1579): Process: com.danlevi.testproject, PID: 1579 
05-16 12:33:37.432: E/AndroidRuntime(1579): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.danlevi.testproject/com.danlevi.testproject.MainActivity}: java.lang.NullPointerException 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.ActivityThread.access$800(ActivityThread.java:135) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.os.Handler.dispatchMessage(Handler.java:102) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.os.Looper.loop(Looper.java:136) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.ActivityThread.main(ActivityThread.java:5017) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at java.lang.reflect.Method.invokeNative(Native Method) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at java.lang.reflect.Method.invoke(Method.java:515) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at dalvik.system.NativeStart.main(Native Method) 
05-16 12:33:37.432: E/AndroidRuntime(1579): Caused by: java.lang.NullPointerException 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at com.danlevi.testproject.MainActivity.onCreate(MainActivity.java:25) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.Activity.performCreate(Activity.java:5231) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159) 
05-16 12:33:37.432: E/AndroidRuntime(1579):  ... 11 more 
05-16 12:33:44.352: I/Process(1579): Sending signal. PID: 1579 SIG: 9

來源

2014-05-16 Dan-Levi Tømta

複製所有內容fragment_main到activity_main.xml..This的方法解決這個問題.. – Lal

這是最簡單和最簡單的解決方案..但正確的做法是在我的答案中指定。首先嚐試我的評論，如果這有助於嘗試我的答案... – Lal

或替換'setContentView（R.layout.activity_main）;'as setContentView R.layout.fragment_main）;' – Lal

這是因爲findViewById（）在activity_main佈局搜索，而按鈕位於該片段的佈局fragment_main。

移動，在片段的onCreateView()方法的代碼：

//... 

View rootView = inflater.inflate(R.layout.fragment_main, container, false); 
Button buttonClick = (Button)rootView.findViewById(R.id.button); 
buttonClick.setOnClickListener(new View.OnClickListener() { 
    @Override 
    public void onClick(View view) { 
     onButtonClick((Button) view); 
    } 
});

注意，現在你訪問它通過rootView view：

Button buttonClick = (Button)rootView.findViewById(R.id.button);

否則你會得到再次NullPointerException。

在你的代碼，移動

changer = (Button) findViewById(R.id.change1); 
changeme = (TextView) findViewById (R.id.changeme1); 
changer.setOnClickListener(new View.OnClickListener() { 

@Override 
public void onClick(View arg0) { 
// TODO Auto-generated method stub 
changeme.setText("Changed"); 
} 
});

到onCreateView()片段

來源

2014-05-16 16:50:54 Lal

謝謝！我把XML移到了activity_main.xml中，並且做到了這一點。接受你的答案。 –

ADT簡單應用程序 - 致命異常

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