L
Linienbusfahrer
Neues Mitglied
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Hallo,
ich bin noch relativ neu in der Android-Entwicklung und als ich vor ein paar Tagen meine erste App schreiben wollte, kamen immer nur Fehler heraus, auch wenn ich den Text 1:1 aus dem Internet kopiere. Ich würde mich sehr freuen, wenn mir jemand erklären könnte, was an meinem Code falsch ist.
MfG
Linienbusfahrer
ich bin noch relativ neu in der Android-Entwicklung und als ich vor ein paar Tagen meine erste App schreiben wollte, kamen immer nur Fehler heraus, auch wenn ich den Text 1:1 aus dem Internet kopiere. Ich würde mich sehr freuen, wenn mir jemand erklären könnte, was an meinem Code falsch ist.
Code:
package com.example.exit;
import android.support.v7.app.ActionBarActivity;
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.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
public class MainActivity extends ActionBarActivity {
Button beendenB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
beendenB = (Button) findViewById(R.id.button1);
beendenB.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
System.exit(0);
}
});
}
@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);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
return rootView;
}
}
}
Code:
<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.exit.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Ich beende das Programm!" />
</RelativeLayout>
Code:
04-19 14:49:18.219: D/AndroidRuntime(2561): Shutting down VM
04-19 14:49:18.219: W/dalvikvm(2561): threadid=1: thread exiting with uncaught exception (group=0xb2aefba8)
04-19 14:49:18.239: E/AndroidRuntime(2561): FATAL EXCEPTION: main
04-19 14:49:18.239: E/AndroidRuntime(2561): Process: com.example.exit, PID: 2561
04-19 14:49:18.239: E/AndroidRuntime(2561): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.exit/com.example.exit.MainActivity}: java.lang.NullPointerException
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.os.Handler.dispatchMessage(Handler.java:102)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.os.Looper.loop(Looper.java:136)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-19 14:49:18.239: E/AndroidRuntime(2561): at java.lang.reflect.Method.invokeNative(Native Method)
04-19 14:49:18.239: E/AndroidRuntime(2561): at java.lang.reflect.Method.invoke(Method.java:515)
04-19 14:49:18.239: E/AndroidRuntime(2561): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-19 14:49:18.239: E/AndroidRuntime(2561): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-19 14:49:18.239: E/AndroidRuntime(2561): at dalvik.system.NativeStart.main(Native Method)
04-19 14:49:18.239: E/AndroidRuntime(2561): Caused by: java.lang.NullPointerException
04-19 14:49:18.239: E/AndroidRuntime(2561): at com.example.exit.MainActivity.onCreate(MainActivity.java:31)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.Activity.performCreate(Activity.java:5231)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-19 14:49:18.239: E/AndroidRuntime(2561): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-19 14:49:18.239: E/AndroidRuntime(2561): ... 11 moreMfG
Linienbusfahrer
