In the main activity you have to call super.onCreate(savedInstanceState) after setContentView()
extending navigation drawer activity to other activities
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19-10-2022 - |
Question
I'm trying to create a navigation drawer activity so I can extend that activity and use the menu in all activities by following the answer given in this question Link but my test app keeps crashing, here's my code:
BaseActivity.java
public class BaseActivity extends Activity {
public DrawerLayout drawerLayout;
public ListView drawerList;
public String[] layers;
private ActionBarDrawerToggle drawerToggle;
protected void onCreate(Bundle savedInstanceState) {
// R.id.drawer_layout should be in every activity with exactly the same
// id.
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerToggle = new ActionBarDrawerToggle((Activity) this, drawerLayout,
R.drawable.ic_drawer, 0, 0) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(R.string.hello_world);
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(R.string.hello_world);
}
};
drawerLayout.setDrawerListener(drawerToggle);
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
layers = getResources().getStringArray(R.array.planets_array);
drawerList = (ListView) findViewById(R.id.left_drawer);
drawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, android.R.id.text1, layers));
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (drawerToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
drawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
drawerToggle.onConfigurationChanged(newConfig);
}
}
MainActivity.java
public class MainActivity extends BaseActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_profile);
}
}
activity_profile.xml
<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=".ProfileActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
</RelativeLayout>
Logcat
03-03 01:22:18.031: D/AndroidRuntime(27902): Shutting down VM
03-03 01:22:18.031: W/dalvikvm(27902): threadid=1: thread exiting with uncaught exception (group=0x2b542210)
03-03 01:22:18.041: E/AndroidRuntime(27902): FATAL EXCEPTION: main
03-03 01:22:18.041: E/AndroidRuntime(27902): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.slider/com.example.slider.MainActivity}: java.lang.NullPointerException
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.access$600(ActivityThread.java:127)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.os.Handler.dispatchMessage(Handler.java:99)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.os.Looper.loop(Looper.java:137)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.main(ActivityThread.java:4441)
03-03 01:22:18.041: E/AndroidRuntime(27902): at java.lang.reflect.Method.invokeNative(Native Method)
03-03 01:22:18.041: E/AndroidRuntime(27902): at java.lang.reflect.Method.invoke(Method.java:511)
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-03 01:22:18.041: E/AndroidRuntime(27902): at dalvik.system.NativeStart.main(Native Method)
03-03 01:22:18.041: E/AndroidRuntime(27902): Caused by: java.lang.NullPointerException
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.example.slider.BaseActivity.onCreate(BaseActivity.java:35)
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.example.slider.MainActivity.onCreate(MainActivity.java:12)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.Activity.performCreate(Activity.java:4465)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
03-03 01:22:18.041: E/AndroidRuntime(27902): ... 11 more
Solution
OTHER TIPS
The problem appears that the base class is not aware of the layout. Not sure how or why it worked for others without having to do something like this.. but I am new to Android.
I was getting the same error and solved by passing my layout to the base via onCreate.
So in the base, I modified onCreate to be like this:
protected void onCreate(Bundle savedInstanceState, int resLayoutID)
{
super.onCreate(savedInstanceState);
setContentView(resLayoutID);
Then, from my new activity, I have this:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState, R.layout.my_activity);
This code in my base now works instead of staying null:
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerList = (ListView) findViewById(R.id.left_drawer);
btw, this result was suggested to me by a friend and it worked for me.
On the parent classBaseActivity:
declare a
protected abstract int getLayoutId();
onCreate() I added the line
setContentView(getLayoutId());
Now implement it on your subclass MainActivity something like:
protected int getLayoutId() {
return R.layout.activity_profile;
}
Please tell me if you know a better solution.
As suggested by oli, you need to call setContentView(R.layout.activity_view) in your main activity.
BaseActivity's onCreate must be called once content view in Main Activity has been set as shown below :
public class BaseActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// REST Navigation drawer initialization
}
}
public class MainActivity extends BaseActivity {
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_view);
super.onCreate(savedInstanceState);
// REST APPLICATION CODE
}
}
Your xml file should look something like this, taken from the android website: http://developer.android.com/training/implementing-navigation/nav-drawer.html
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The main content view -->
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<!-- Add content here -->
</FrameLayout>
<!-- The navigation drawer -->
<ListView android:id="@+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp"
android:background="#111"/>
</android.support.v4.widget.DrawerLayout>
In you MainActivity just put set setContentView(R.layout.activity_main)
before
super.onCreate(savedInstanceState);
like below:
@Override
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_profile);
super.onCreate(savedInstanceState);
}