I'm beginner in android development. I get this error message both in emulator and my real Android device. Please help me !!
public class MainActivity extends ActionBarActivity {
Button btn1;
TextView tv1;
EditText edt1;
String msj= "d";
double n = Double.valueOf(edt1 . getText().toString());
double a = (1 / (Math.sqrt(5)));
double b = ((1+(Math.sqrt(5)))/2);
double c = ((1-(Math.sqrt(5)))/2);
double i = a * ((Math.pow(b,n)) - (Math.pow(c,n)));
String k = String.valueOf(i);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn1 = (Button) findViewById(R.id.btn1);
final TextView tv1 = (TextView) findViewById(R.id.tv1);
final EditText edt1 = (EditText) findViewById(R.id.edt1);
btn1.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
msj = edt1.getText().toString();
tv1.setText( k );
}
});
}
@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);
}
}
XML 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.fibonacci.MainActivity" >
<EditText
android:id="@+id/edt1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:ems="10"
android:hint="@string/girdi"
android:inputType="number" >
</EditText>
<Button
android:id="@+id/btn1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/edt1"
android:layout_centerHorizontal="true"
android:layout_marginTop="60dp"
android:text="@string/buton" />
<TextView
android:id="@+id/tv1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignLeft="@+id/edt1"
android:layout_below="@+id/btn1"
android:layout_marginTop="37dp"
android:text="@string/cikti" />
</RelativeLayout>
I could't able to post the Log cat. Because of character limitation. HEre is the LogCat:
0-13 17:10:48.907: I/Choreographer(380): Skipped 30 frames! The application may be doing too much work on its main thread.
10-13 17:10:48.927: E/AndroidRuntime(1021): FATAL EXCEPTION: main
10-13 17:10:48.927: E/AndroidRuntime(1021): Process: com.example.fibonacci, PID: 1021
10-13 17:10:48.927: E/AndroidRuntime(1021): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.fibonacci/com.example.fibonacci.MainActivity}: java.lang.NullPointerException
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.app.ActivityThread.access$800(ActivityThread.java:135)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.os.Handler.dispatchMessage(Handler.java:102)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.os.Looper.loop(Looper.java:136)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.app.ActivityThread.main(ActivityThread.java:5017)
10-13 17:10:48.927: E/AndroidRuntime(1021): at java.lang.reflect.Method.invokeNative(Native Method)
10-13 17:10:48.927: E/AndroidRuntime(1021): at java.lang.reflect.Method.invoke(Method.java:515)
10-13 17:10:48.927: E/AndroidRuntime(1021): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
10-13 17:10:48.927: E/AndroidRuntime(1021): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
10-13 17:10:48.927: E/AndroidRuntime(1021): at dalvik.system.NativeStart.main(Native Method)
10-13 17:10:48.927: E/AndroidRuntime(1021): Caused by: java.lang.NullPointerException
10-13 17:10:48.927: E/AndroidRuntime(1021): at com.example.fibonacci.MainActivity.<init>(MainActivity.java:20)
10-13 17:10:48.927: E/AndroidRuntime(1021): at java.lang.Class.newInstanceImpl(Native Method)
10-13 17:10:48.927: E/AndroidRuntime(1021): at java.lang.Class.newInstance(Class.java:1208)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
10-13 17:10:48.927: E/AndroidRuntime(1021): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
10-13 17:10:48.927: E/AndroidRuntime(1021): ... 11 more
10-13 17:10:48.977: I/Choreographer(380): Skipped 47 frames! The application may be doing too much work on its main thread.
10-13 17:10:48.977: W/ActivityManager(380): Force finishing activity com.example.fibonacci/.MainActivity
10-13 17:10:49.387: I/WindowManager(380): Screenshot max retries 4 of Token{b2f8e630 ActivityRecord{b2f8e4d0 u0 com.example.fibonacci/.MainActivity t3 f}} appWin=Window{b30e4a38 u0 Starting com.example.fibonacci} drawState=4
10-13 17:10:49.387: W/WindowManager(380): Screenshot failure taking screenshot for (320x480) to layer 21010
Thanks for your help.
As @Sunil made a point, this is probably gonna get you closer to your code to work. You have to calculate in your onClick method.
public class MainActivity extends ActionBarActivity {
Button btn1;
TextView tv1;
EditText edt1;
String msj= "d";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn1 = (Button) findViewById(R.id.btn1);
tv1 = (TextView) findViewById(R.id.tv1);
edt1 = (EditText) findViewById(R.id.edt1);
btn1.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
double n = Double.valueOf(edt1.getText().toString());
double a = (1 / (Math.sqrt(5)));
double b = ((1+(Math.sqrt(5)))/2);
double c = ((1-(Math.sqrt(5)))/2);
double i = a * ((Math.pow(b,n)) - (Math.pow(c,n)));
String k = String.valueOf(i);
msj = edt1.getText().toString();
tv1.setText( k );
}
});
}
}