android activity crashes for no reason ? maybe because of setcontentview? - android-activity

Question

i'm having an issue with android development (i'm a newbiew btw) ..
i'm trying to accomplish this tutorial : http://developer.android.com/training/basics/firstapp/starting-activity.html, except that my problem is that the second activity crashes systematically and i dont know why ..
when i comment the line : setContentView(textView1): the second activity doesnt crash, but the text is not shown . so i guess thats where my problem is , but i have been looking for hours and i cant seem to figure it out :-s
here's my code :
(main activity) XML Layout: :
<RelativeLayout "
android:id="#+id/texttoto"
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.toto.MainActivity$PlaceholderFragment" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/hello_world" />
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/editText_mail"
android:layout_alignLeft="#+id/editText_mail"
android:onClick="test_trucs"
android:text="#string/test" />
<EditText
android:id="#+id/txttopass"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/textView1"
android:layout_below="#+id/textView1"
android:layout_marginTop="15dp"
android:ems="10"
android:hint="#string/texttopass" >
</EditText>
</RelativeLayout>
**(second activity) XML Layout:* :*
<RelativeLayout "
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.toto.Blabla$PlaceholderFragment" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/hello_world" />
</RelativeLayout>
****MainActivity.JAVA:****
package com.toto;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity {
public final static String EXTRA_MESSAGE = "com.toto.MESSAGE";
#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();
}
}
#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;
}
}
/** mettre les class ICI **/
public void test_trucs(View view) {
Intent intent = new Intent(this, Blabla.class);
EditText editText = (EditText) findViewById(R.id.txttopass);
String message = editText.getText().toString();
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
}
}
****Blabla.JAVA:****
package com.toto;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class Blabla extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_blabla);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
// Get the message from the intent
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
// Create the text view
TextView textView1 = new TextView(this);
textView1.setTextSize(40);
textView1.setText(message);
// Set the text view as the activity layout
setContentView(textView1);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.blabla, 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_blabla,
container, false);
return rootView;
}
}
}
the logcat show this :
06-19 15:35:47.982: E/AndroidRuntime(22378): FATAL EXCEPTION: main
06-19 15:35:47.982: E/AndroidRuntime(22378): Process: com.toto, PID: 22378
06-19 15:35:47.982: E/AndroidRuntime(22378): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.toto/com.toto.Blabla}: java.lang.NullPointerException
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.ActivityThread.access$800(ActivityThread.java:135)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.os.Handler.dispatchMessage(Handler.java:102)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.os.Looper.loop(Looper.java:136)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.ActivityThread.main(ActivityThread.java:5001)
06-19 15:35:47.982: E/AndroidRuntime(22378): at java.lang.reflect.Method.invokeNative(Native Method)
06-19 15:35:47.982: E/AndroidRuntime(22378): at java.lang.reflect.Method.invoke(Method.java:515)
06-19 15:35:47.982: E/AndroidRuntime(22378): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
06-19 15:35:47.982: E/AndroidRuntime(22378): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
06-19 15:35:47.982: E/AndroidRuntime(22378): at dalvik.system.NativeStart.main(Native Method)
06-19 15:35:47.982: E/AndroidRuntime(22378): Caused by: java.lang.NullPointerException
06-19 15:35:47.982: E/AndroidRuntime(22378): at com.toto.Blabla.onCreate(Blabla.java:39)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.Activity.performCreate(Activity.java:5231)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
06-19 15:35:47.982: E/AndroidRuntime(22378): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
06-19 15:35:47.982: E/AndroidRuntime(22378): ... 11 more
i know this is probably the newbiest thing ever, but please be indulgent ..
thanks in advance for the help !

Answer 1

You are calling setContentView twice, the first:
setContentView(R.layout.activity_blabla);
Isn't in the tutorial. I'm not sure what's exactly causing the NullPointer exception, but it seems that calling that twice can cause problems.
If you want to use a more complex layout (R.layout_blabla), and show the message, like it seems to be your case as the text view is in that layout, reference it from the onCreate by findViewById, instead of create a new TextView
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_blabla);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
// Get the message from the intent
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
// Create the text view
TextView textView1 = (TextView)findViewById(R.id.textView1)
textView1.setTextSize(40);
textView1.setText(message);
// Set the text view as the activity layout
setContentView(textView1);
}