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Classcastexception: Widget cannot be cast to layout

Though this tends to be very basic question, i cannot solve this issue. I searched the similar kind of issue but none solves my issue.
I created my own class where i created some basic controls and i called this class in my xml as
<com.mypackagename.classname
..
..
/>
and some views goes inside this. and before this now i would like to add relativelayout as
activity_main1.xml:
<RelativeLayout xmlns:android="schemas.android.com/apk/res/android"
xmlns:android1="http://schemas.android.com/apk/res/android"
android1:layout_width="match_parent"
android1:layout_height="wrap_content" >
<com.test.MainLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/mainlayout"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView
android:id="#+id/drawer_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:src="#drawable/ic_drawer" />
</LinearLayout>
</com.test.MainLayout>
</RelativeLayout >
and i my main activity i declared as
MainActivity:
Myview view;
view = (Myview)this.getLayoutInflater().inflate(R.layout.activity_main1, null);
setContentView(view);
where MyView is the class where i have my own controls.
After adding relative layout i tried something like
MainActivity1.java:
public class MainActivity1 extends FragmentActivity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
RelativeLayout item = (RelativeLayout)findViewById(R.id.item);
view = (Myview)this.getLayoutInflater().inflate(R.layout.activity_main1, null);
item.addView(view);
setContentView(item); // facing an error here
.......... rest of the code
}
and my layout activity is
public class MainLayout1 extends LinearLayout
{
....
}
while running it is throwing classcastexception and the error is
java.lang.ClassCastException: android.widget.RelativeLayout cannot be cast to com.view.layout.MainLayout

view = (Myview)this.getLayoutInflater().inflate(R.layout.activity_main1, null);
At this point in your java class, you are getting MyView Object in view, but it is actually a layout file instance which returns its parent layout here its a RelativeLayout.
Since inflate(R.layout.activity_main1, null); returns the object of RelativeLayout. Instead of this you have to get instance of your MainLayout1 like(R.id.mainlayout) and then cast it into the MyView object like:
RelativeLayout item = (View)this.getLayoutInflater().inflate(R.layout.activity_main1,null);
view = (Myview) item.findViewById(R.id.mainlayout);
item.addView(view);
setContentView(item);

Alternatives to creating a Compound Control by extending a Layout

I want to create a custom Compound Control in Android that holds some logic. For the purpose of this example, let's say I want it to switch between two views when clicked.
According to the API guide, it looks like the way to do that is to create a new class that extends Layout, and do everything in there.
So I did just that:
I created a XML layout to inflate for my custom component:
.
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/view1"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="Hello"/>
<TextView
android:id="#+id/view2"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="World"
android:visibility="gone"/>
</RelativeLayout>
Then I created my custom Layout class, and added the logic in there:
public class MyWidget extends RelativeLayout {
public final View mView1;
public final View mView2;
public MyWidget(Context context, AttributeSet attrs) {
super(context, attrs);
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
RelativeLayout view = (RelativeLayout) inflater.inflate(R.layout.my_widget, this, true);
mView1 = view.findViewById(R.id.view1);
mView2 = view.findViewById(R.id.view2);
view.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
switchViews();
}
});
}
public void switchViews() {
if (mView1.getVisibility() == View.VISIBLE) {
mView1.setVisibility(View.GONE);
} else {
mView1.setVisibility(View.VISIBLE);
}
if (mView2.getVisibility() == View.VISIBLE) {
mView2.setVisibility(View.GONE);
} else {
mView2.setVisibility(View.VISIBLE);
}
}
}
And finally, I included my custom view in some layout:
.
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.example.MyWidget
android:layout_height="match_parent"
android:layout_width="match_parent"/>
</RelativeLayout
And that works.
I am not completely happy with that solution though, for 2 reasons:
In the constructor of MyWidget, I instantiate 2 nested RelativeLayout by calling the super() constructor, and the one that is at the root of my XML layout. For that, I know I can instead use <merge> as my XML root and that gets me rid of the extra RelativeLayout. Except that defining XML attributes, such as android:background on my <merge> tag doesn't have any effect, so I have to define it programmatically, which is not as nice.
The custom View is a subclass of RelativeLayout, and therefore expose methods it inherits from it, such as addView(), even if it doesn't make sense to add child views to it. I know I can override those methods to prevent users from doing that, but I would still find it cleaner to inherit from View.

How to implement Custom View as part of MVC?

So I'm experimenting with implementing an MVC pattern in Android where my views are subclassed from RelativeLayout, LinearLayout, ScrollView, etc... It's working until I try to get a hold of a view within my view. I get an NPE. I've tried accessing the view in order to set the onClickListener in the constructor and also in onAttachedToWindow(), but I get the NPE in both places.
For example, here's a view class:
public class ViewAchievements extends LinearLayout
{
private RelativeLayout mRelativeLayoutAchievement1;
public ViewAchievements(Context context, AttributeSet attrs)
{
super(context, attrs);
mRelativeLayoutAchievement1 = (RelativeLayout) findViewById(R.id.relativeLayout_achievement1);
mRelativeLayoutAchievement1.setOnClickListener((OnClickListener) context); //NPE on this line
}
#Override
protected void onAttachedToWindow()
{
super.onAttachedToWindow();
mRelativeLayoutAchievement1.setOnClickListener(mOnClickListener); //Also get NPE on this line
}
}
Can someone please tell me the proper way to get a hold of my subviews, in this case mRelativeLayoutAchievement1?
Here's an XML snippet:
<com.beachbody.p90x.achievements.ViewAchievements xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#color/gray_very_dark"
android:orientation="vertical" >
<!-- kv Row 1 -->
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="0dp"
android:orientation="horizontal"
android:layout_weight="1"
android:baselineAligned="false">
<RelativeLayout
android:id="#+id/relativeLayout_achievement1"
style="#style/linearLayout_achievement"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_margin="#dimen/margin_sm"
android:layout_weight="1" >
<TextView
android:id="#+id/textView_achievement1"
style="#style/text_small_bold_gray"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="#dimen/margin_large"
android:text="1/20" />
</RelativeLayout>
...
And here's how I'm creating the view from my Activity:
public class ActivityAchievements extends ActivitySlidingMenu
{
private ViewAchievements mViewAchievements;
#Override
public void onCreate(Bundle savedInstanceState)
{
mViewAchievements = (ViewAchievements) View.inflate(this, R.layout.view_achievements, null);
setContentView(mViewAchievements);
...

You're trying to get the child views during the view's constructor. Since they are child views, they haven't been inflated yet. Can you move this code out of the constructor, possibly into View.onAttachedToWindow()?
http://developer.android.com/reference/android/view/View.html#onAttachedToWindow()

Communication between custom SurfaceView and default android's views

My problem is communication between custom GameView (extends SurfaceView) and TextView: I want to set TextView's text from inside of the GameView.
In main activity i'm using this layout file, it should explain structure of my app:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#00ff00"
>
<TextView
android:id="#+id/scoreTV"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="score: 0"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="back"
android:layout_alignParentRight="true" />
</RelativeLayout>
<org.gk.grApp.GameView
android:id="#+id/gameplayScreen"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
</LinearLayout>
I can't change TextView's text in my GameView object, because it's impossible to touch UI thread from another.
Handler doesn't work too, because i can't give a handler's reference to GameView's constructor, that is performed after loading this xml file (a read about default constructor for xml files eg here How can I use GLSurfaceView in a LinearLayout together with other Views, such as TextView or Button?).
Do you have any idea what I should do now? Maybe my deduction is wrong, so please, tell me about this.
EDIT: I changed my xml file, instead of GameView I have now:
<LinearLayout
android:id="#+id/gameplayScreen"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
</LinearLayout>
Also I added an argument (third) into constructor's signature:
public GameView(Context context, AttributeSet as, Handler h) { ... }
and changed my onCreate in GameplayActivity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.gameplay);
LinearLayout ll = (LinearLayout)findViewById(R.id.gameplayScreen);
GV = new GameView(this, null, scoreHandler);
ll.addView(GV);
}
It works, now I can set TextView's text but after clicking on the back button another exception is thrown:
"Performing pause of activity that is not resumed: {org.gk.grApp/org.gk.grApp.MainMenuActivity}". I just started searching information about this.

First make a reference to the TextView on the activity level:
TextView txv;
In onCreate assign this reference:
txv = (TextView) findViewById(R.id.MyTextView);
Then make a method in your Activity after onCreate like this:
public void setTextView(final String txt){
MyActivity.this.runOnUiThread(new Runnable() {
public void run() {
txv.setText(txt);
}
});
}
Then you make a call from your custom view:
((MyActivity) getContext()).setTextView(str);

How to create reusable xml wrappers for Android Layout files

I have several layout files that are mostly the same, except for one section. Is there a way that I can have the common XML all in one place; instead of copy/pasting, and having to update a bunch of files when I want to make 1 change?
I know that I can include XML from other XML files, but the common code isn't an internal control; it is the outer wrapper; so include doesn't work. Basically, I have a bunch of files that all look like this:
<LinearLayout
android:id="#+id/row"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal">
<ImageView android:layout_height="26dp"
android:id="#+id/checkImage"
android:layout_width="26dp"
android:layout_alignParentTop="true"
android:scaleType="fitCenter"/>
<!-- Different types of views go here depending on which layout file it is -->
<ImageButton android:layout_height="fill_parent"
android:id="#+id/playButton"
android:layout_width="42dp"
android:src="#drawable/play_button"
android:scaleType="center"
android:background="#00000000"/>
</LinearLayout>
Basically, I want to do what ASP.Net does with Master Pages. Is there any option for this?

The solution was pretty easy.
You need to extend "Activity" Class, in onCreate() function SetContentView to your base xml layout and also need to override setContentView in base Activity Class
For Example:
1.Create base_layout.xml with the below code
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:id="#+id/image_view_01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:maxHeight="50dp" />
</LinearLayout>
<LinearLayout
android:id="#+id/base_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</LinearLayout>
</LinearLayout>
Create BaseActivity.java
public class BaseActivity extends Activity {
ImageView image;
LinearLayout baseLayout;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
super.setContentView(R.layout.base_layout);
this.image = (ImageView) this.findViewById(R.id.image_view_01);
this.baseLayout = (LinearLayout) this.findViewById(R.id.base_layout);
this.image.setImageResource(R.drawable.header);
}
#Override
public void setContentView(int id) {
LayoutInflater inflater = (LayoutInflater)getBaseContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater.inflate(id, this.baseLayout);
}
}
and SomeActivity.java
public class SomeActivity extends BaseActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
super.setContentView(R.layout.some_layout);
//rest of code
}
}
The only thing I noticed so far was that when requesting a progress bar (requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS)) this needs to be done before calling super.onCreate. I think this is because nothing can be drawn yet before calling this function.
This worked great for me and hopefully you will find this useful in your own coding.

Maybe you could use one main layout XML file and then add/remove other widgets dynamically through code as needed.

I was trying to do exactly this - I wanted a view that had a button on the left and a button on the right, but could have arbitrary content in the middle (depending on who was including it). Basically a custom view group that could have child view in the XML layout, and would wrap those child views with another XML layout. Here is how I did it:
top_bar.xml: This represents the common layout to wrap things with. Note the LinearLayout (could be any layout) with an ID "addChildrenHere" - it is referenced later.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/topBarLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="left" />
<LinearLayout
android:id="#+id/addChildrenHere"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"/>
<Button
android:id="#+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="right" />
</LinearLayout>
main.xml: The main layout. This includes a custom viewgroup (WrappedLayout) with a few children. Note how it declares a custom XML namespace, and sets two custom attributes on the WrappedLayout tag (these say which layout to wrap the children with, and where within that layout the children of this node should be placed).
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:karl="http://schemas.android.com/apk/res/karl.test"
android:id="#+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<karl.test.WrappedLayout
android:id="#+id/topBarLayout1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
karl:layoutToInflate="#layout/top_bar"
karl:childContainerID="#+id/addChildrenHere">
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="This is a child of the special wrapper."
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="#+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="This is another child; you can put anything here."
android:textAppearance="?android:attr/textAppearanceMedium" />
</karl.test.WrappedLayout>
</LinearLayout>
attrs.xml: This goes in res/values. This defines the custom XML attributes used in the XML above.
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="WrappedLayout">
<attr name="layoutToInflate" format="integer"/>
<attr name="childContainerID" format="integer"/>
</declare-styleable>
</resources>
Finally, WrappedLayout.java: This handles reading the custom attributes, and doing a bit of hackery to make addView() actually add the views in a different place.
package karl.test;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
public class WrappedLayout extends FrameLayout
{
///Attempts to add children to this layout will actually get forwarded through to mChildContainer.
///This would be final, but it's actually used indirectly by the constructor before it's initialised.
private ViewGroup mChildContainer;
public WrappedLayout(Context context, AttributeSet attrs)
{
super(context, attrs);
//read the custom attributes
final int layoutToInflate;
final int childContainerID;
{
final TypedArray styledAttributes = context.obtainStyledAttributes(attrs, R.styleable.WrappedLayout);
layoutToInflate = styledAttributes.getResourceId(R.styleable.WrappedLayout_layoutToInflate, 0);
childContainerID = styledAttributes.getResourceId(R.styleable.WrappedLayout_childContainerID, 0);
styledAttributes.recycle();
}
if(layoutToInflate == 0
|| childContainerID == 0)
{
Log.e("Error", "WrappedLayout.WrappedLayout(): Error reading custom attributes from XML. layoutToInflate = " + layoutToInflate + ", childContainerID =" + childContainerID);
}
else
{
//inflate the layout and (implicitly) add it as a child view
final View inflatedLayout = View.inflate(context, layoutToInflate, this);
//grab the reference to the container to pass children through to
mChildContainer = (ViewGroup)inflatedLayout.findViewById(childContainerID);
}
}
///All the addView() overloads eventually call this method.
#Override
public void addView(View child, int index, ViewGroup.LayoutParams params)
{
if(mChildContainer == null)
{
//still inflating - we're adding one of the views that makes up the wrapper structure
super.addView(child, index, params);
}
else
{
//finished inflating - forward the view through to the child container
mChildContainer.addView(child, index, params);
}
}
}
This works, as far as I can tell. It doesn't work very well with the Eclipse layout editor (I'm not quite sure what the problem is), but you can view the layout fine. Changing the children of the WrappedLayout seems to require editing the XML manually.

Have you looked at Applying Styles and Themes?