java.lang.RuntimeException：無法啓動活動

我在努力學習如何爲Android創建應用程序。繼教程，我的修改提出了by Google我得到這個錯誤java.lang.RuntimeException：無法啓動活動

12-26 10:42:23.848: D/dalvikvm(1302): GC_CONCURRENT freed 362K, 15% free 2737K/3216K, paused 70ms+89ms, total 204ms 
12-26 10:42:23.898: D/AndroidRuntime(1302): Shutting down VM 
12-26 10:42:23.898: W/dalvikvm(1302): threadid=1: thread exiting with uncaught exception (group=0x40a70930) 
12-26 10:42:23.928: E/AndroidRuntime(1302): FATAL EXCEPTION: main 
12-26 10:42:23.928: E/AndroidRuntime(1302): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.startactivity/com.example.startactivity.DisplayMessageActivity}: java.lang.NullPointerException 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java: 1234) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.os.Handler.dispatchMessage(Handler.java:99) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.os.Looper.loop(Looper.java:137) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.ActivityThread.main(ActivityThread.java:5039) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at java.lang.reflect.Method.invokeNative(Native Method) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at java.lang.reflect.Method.invoke(Method.java:511) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at dalvik.system.NativeStart.main(Native Method) 
12-26 10:42:23.928: E/AndroidRuntime(1302): Caused by: java.lang.NullPointerException 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at com.example.startactivity.DisplayMessageActivity.onCreate(DisplayMessageActivity.java:20) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.Activity.performCreate(Activity.java:5104) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
12-26 10:42:23.928: E/AndroidRuntime(1302):  ... 11 more 
12-26 10:43:11.418: I/Process(1302): Sending signal. PID: 1302 SIG: 9

這是MainActivity

public class MainActivity extends Activity { 
public final static String EXTRA_MESSAGE = "com.example.startactivity.MESSAGE"; 

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

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

public void sendMessage(View view){ 
    Intent intent = new Intent(this,DisplayMessageActivity.class); 

    EditText edit_nome = (EditText) findViewById(R.id.edit_nome); 
    EditText edit_cognome = (EditText) findViewById(R.id.edit_cognome); 

    Bundle bundle = new Bundle(); 
    bundle.putString("nome", edit_nome.getText().toString()); 
    bundle.putString("cognome", edit_cognome.getText().toString()); 

    intent.putExtra(EXTRA_MESSAGE, bundle); 
    startActivity(intent); 


} 

}

的代碼這是DisplayMessageActivity的代碼

public class DisplayMessageActivity extends Activity { 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_display_message); 
    // Show the Up button in the action bar. 
    getActionBar().setDisplayHomeAsUpEnabled(true); 

    Intent intent = getIntent(); 
    String nome = intent.getBundleExtra("nome").toString(); 
    String cognome = intent.getBundleExtra("cognome").toString(); 

    TextView textNome = new TextView(this); 
    TextView textCognome = new TextView(this); 
    textNome.setTextSize(40); 
    textCognome.setTextSize(40); 
    textNome.setText(nome); 
    textCognome.setText(cognome); 

    setContentView(textNome); 
    setContentView(textCognome); 


} 


@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
    case android.R.id.home: 
     NavUtils.navigateUpFromSameTask(this); 
     return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 

}

感謝您的幫助。

來源

2012-12-26 Cezar Sas

問題並非runtimeexception，它是一個簡單的NPE。看看給出的行號，那裏的東西是空的。 – njzk2

@ForcelTA您是否嘗試過使用下面的發佈解決方案。這將解決你的問題。謝謝。 –

要調用的Bundle的toString方法，而不是檢索存儲在它的字符串。另外，您正嘗試使用存儲在其中的密鑰獲取Bundle。嘗試chaning考慮

String nome = intent.getBundleExtra("nome").toString(); 
String cognome = intent.getBundleExtra("cognome").toString();

到

Bundle bundle = intent.getBundleExtra(MainActivity.EXTRA_MESSAGE); 

if (bundle != null) { 
    String nome = bundle.getString("nome"); 
    String cognome = bundle.getString("cognome"); 
}

走，如果收到的意圖是不是你的，它帶有沒有Bundle，或者不同的地方，你nome和cognome字符串會null，不是空的字符串。

來源

2012-12-26 11:30:36 JoseLSegura

完美的作品。感謝您的幫助 –

歡迎您:-) – JoseLSegura

變化MainActivity代碼

public class MainActivity extends Activity { 
    public final static String EXTRA_MESSAGE = "com.example.startactivity.MESSAGE"; 

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

Intent intent = new Intent(this,DisplayMessageActivity.class); 

EditText edit_nome = (EditText) findViewById(R.id.edit_nome); 
EditText edit_cognome = (EditText) findViewById(R.id.edit_cognome); 

Bundle bundle = new Bundle(); 
bundle.putString("nome", edit_nome.getText().toString()); 
bundle.putString("cognome", edit_cognome.getText().toString()); 

intent.putExtra(EXTRA_MESSAGE, bundle); 
startActivity(intent); 


} 

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


}

製作清單文件，確保該條目：

<activity android:name=".DisplayMessageActivity"></activity>

來源

2012-12-26 11:15:30

的logcat的顯示AT- com.example.startactivity/com.example.startactivity問題。 DisplayMessageActivity

所以，最好的猜測是nome和cognome的值可能是null，在你設置texviews中的文本在DisplayMessageActivity

嘗試添加調試點在該行文本

String nome = intent.getBundleExtra("nome").toString();

，並查看任何空值。

希望這jelps

來源

2012-12-26 11:20:39

java.lang.RuntimeException：無法啓動活動

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