I'm beginner in android, OnClickListener generates exception, can any one help me out, if i have code commented then I dont see any exception ?
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.*;
import android.widget.*;
public class MainActivity extends ActionBarActivity {
@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();
}
/*
Button calc = (Button) findViewById(R.id.calcButton);
calc.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
EditText leftnum = (EditText) findViewById(R.id.leftnum);
EditText rightnum = (EditText) findViewById(R.id.rightnum);
//EditText func = (EditText) findViewById(R.id.func);
TextView result = (TextView) findViewById(R.id.result);
double leftnumdouble = Double.parseDouble(leftnum.getText().toString());
double rightnumdouble = Double.parseDouble(rightnum.getText().toString());
double resultnumdouble = leftnumdouble+rightnumdouble;
result.setText(resultnumdouble + "");
}
});
*/
}
@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;
}
}
}
Here's the layout I'm using:
<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.prkh.calculator.MainActivity$PlaceholderFragment" >
<EditText
android:id="@+id/leftnum"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="2dp"
android:ems="5"
android:inputType="numberDecimal" />
<EditText
android:id="@+id/func"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/leftnum"
android:layout_below="@+id/leftnum"
android:layout_marginTop="30dp"
android:ems="1"
android:inputType="text"
android:maxLength="1" />
<EditText
android:id="@+id/rightnum"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/func"
android:layout_below="@+id/func"
android:layout_marginTop="30dp"
android:ems="5"
android:inputType="numberDecimal" />
<Button
android:id="@+id/calcButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/rightnum"
android:layout_below="@+id/rightnum"
android:layout_marginTop="30dp"
android:text="Calculate" />
<TextView
android:id="@+id/result"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/calcButton"
android:layout_below="@+id/calcButton"
android:layout_marginTop="60dp"
android:ems="10">
</TextView>
</RelativeLayout>
And this is the logcat:
05-15 05:18:33.708: D/AndroidRuntime(1682): Shutting down VM
05-15 05:18:33.708: W/dalvikvm(1682): threadid=1: thread exiting with uncaught exception (group=0xb2accba8)
05-15 05:18:33.748: E/AndroidRuntime(1682): FATAL EXCEPTION: main
05-15 05:18:33.748: E/AndroidRuntime(1682): Process: com.prkh.calculator, PID: 1682
05-15 05:18:33.748: E/AndroidRuntime(1682): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.prkh.calculator/com.prkh.calculator.MainActivity}:
java.lang.NullPointerException
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.ActivityThread.access$800(ActivityThread.java:135)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.os.Handler.dispatchMessage(Handler.java:102)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.os.Looper.loop(Looper.java:136)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.ActivityThread.main(ActivityThread.java:5017)
05-15 05:18:33.748: E/AndroidRuntime(1682): at java.lang.reflect.Method.invokeNative(Native Method)
05-15 05:18:33.748: E/AndroidRuntime(1682): at java.lang.reflect.Method.invoke(Method.java:515)
05-15 05:18:33.748: E/AndroidRuntime(1682): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-15 05:18:33.748: E/AndroidRuntime(1682): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-15 05:18:33.748: E/AndroidRuntime(1682): at dalvik.system.NativeStart.main(Native Method)
05-15 05:18:33.748: E/AndroidRuntime(1682): Caused by: java.lang.NullPointerException
05-15 05:18:33.748: E/AndroidRuntime(1682): at com.prkh.calculator.MainActivity.onCreate(MainActivity.java:24)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.Activity.performCreate(Activity.java:5231)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-15 05:18:33.748: E/AndroidRuntime(1682): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
05-15 05:18:33.748: E/AndroidRuntime(1682): ... 11 more
05-15 05:18:38.548: I/Process(1682): Sending signal. PID: 1682 SIG: 9
05-15 05:20:17.218: D/(1731): HostConnection::get() New Host Connection established 0xb8b90680, tid 1731
05-15 05:20:17.378: W/EGL_emulation(1731): eglSurfaceAttrib not implemented
05-15 05:20:17.398: D/OpenGLRenderer(1731): Enabling debug mode 0
05-15 05:20:24.608: I/Choreographer(1731): Skipped 31 frames! The application may be doing too much work on its main thread.
05-15 05:20:27.458: W/IInputConnectionWrapper(1731): showStatusIcon on inactive InputConnection
