In an Android application, I have created a custom view extending the View class. I want to declare an object of my class in the xml layout file but, even after many tries, the application unexpectedly stops when the setContentView call is executed (that's what the popup windows which appears says).
In my view class, which is declared in my MainActivity file as public, I have two constructors : one with only the Context as parameter and one with a Context and an AttributeSet parameters. And I have overridden the onDraw function.
This class is in my source package, named org.me.myapp.
In the layout file, I declare the object I want to insert like this :
<org.me.myApp.MainActivity.myView"
android:id="#+id/View"
android:layout_below="#id/toto"
android:layout_width="300dip"
android:layout_height="100dip"/>
Can anyone tell me what is wrong?
Thanks in advance for the time you will spend trying to help me.
What Yar said, you should extend View or ViewGroup to create custom layout element, and use that class name in your layout xml. Not member variable what it looks you're trying to do. After inflating your layout you can access your custom view with;
org.me.myapp.MyView myView = (org.me.myapp.MyView) findViewById(R.id.MYVIEWID);
I think you need to declare your custom layout as a separate class, for example: org.me.myapp.MyView and relate to it in your xml file like this:
<org.me.myapp.MyView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
...
/>
Related
I notice that there is a tag <view>(not <View>) which can be used in Android layout xml. When I add such a tag in a layout xml, the app can be successfully compiled but crashes when running. So what is this <view> used for?
view is an alternative way for specifying a view to inflate. You need to combine it with class attribute to specify the class name.
This is "useful" if your view class is an inner class and you cannot use something with a $ in the tag name in XML. (Having inner classes as Views you inflate is not a very good idea though.)
For example:
<view class="your.app.full.package.Something$InnerClass" ... />
Reference: http://androidxref.com/5.0.0_r2/xref/frameworks/base/core/java/android/view/LayoutInflater.java#696
View is widget of android that is use to add any kind of view.Like in problems when we use scrollView in a activity and at bottom of activity there is buttons ,That time we add view to looks better.We can set any kind of color to View .
for exp
This will make a View of 20dp height.
I have a custom component that actually wraps another component. Its layout is:
<AutoCompleteTextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent"
android:background="#drawable/text_view_background" android:textCursorDrawable="#null"
android:textColor="#android:color/black" android:inputType="textNoSuggestions"
android:paddingLeft="7dp"/>
In the component's code I'm trying to inflate it:
inflate(context,R.layout.results_auto_complete,this);
resultsAutoComplete=(AutoCompleteTextView)getChildAt(0);
But I'm getting a ClassCastException and it says the first child is a RelativeLayout! I traced all the children of this relative layout and it's actually the layout of the widget whose configuration activity contains my custom component! When I tested the component with a simple test activity everything worked!
So why is it happening and what can I do about this?
Thanks.
If your AutoCompleteTextView is a standalone xml file (your code is the root xml tag) of results_auto_complete.xml. It is the result of the inflation, NO need to use getChildAt(i).
if <AutoCompleteTextView> is a child element in an XML file, use should assign it an Id: android:id="#+id/your_view_id". Then after the inflation, use:
this.findViewById(R.your_view_id);
where this is current activity which loads the component view.
Update, try this:
LayoutInflater mInflater = (LayoutInflater)etContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
resultsAutoComplete=(AutoCompleteTextView)mInflater.inflate(R.layout.your_view_id, this, true);
It seems the problem is that I have 2 layouts with the same identifiers from different projects (one project is linked to the other), so when I'm trying to inflate a layout from one of the projects, I'm getting the layout with the same identifier in the other project. Anyway, thanks for trying to help.
When declaring custom view in xml, what is the difference between declaring a View of a custom class, or declaring a completely custom view:
<LinearLayout>
<view class="packageName.MyView" android:id="#+id/myView" />
</LinearLayout>
and
<LinearLayout>
<packageName.myView android:id="#+id/myView" />
</LinearLayout>
?
I've created a subclass of EditText, and when instatiating it as View class=".." my Activity crashes with ClassCastException when trying to access MyView:
(MyView) myView = (MyView) findViewById(R.id.myView);
When declared as second option, everything works as expected.
I'm not 100% sure on this, but let me give it a go. A couple of things could be happening. The parser might not understand the class attribute correctly (e.g. it thinks it is part of a stylesheet). I am not sure how the parser handles the class attribute, since I have never seen or used it (in fact, I've never seen the <View> tag used either). A better explanation, though, might be this: the parser is trying to down-cast your View into packageName.myView class and fails (down-casting is always risky; up-casting is always safe).
Regardless of what is happening, I would always use the second option you listed, <packageName.myView android:id...>, instead of using the <View> tag. Reason being, it's redundant to use the <View> tag. Everything in this xml file must be a view (LinearLayout, Button, TextView, etc. are all descendants of the View class).
Hope that helps. If you're really, really curious, you could always download the source code for the parser...
I'm coming from the world of GWT and UIBinder, where I'm used to defining custom components by extending Composite, and then putting all the UI layout code in a MyComponent.ui.xml file. This is a very nice way to build up components from smaller pieces.
I'm trying to achieve the same effect on Android with custom Views. I've been able to programmatically extend View, and then add objects by calling addView(textView). I'd like to be able to do that in XML, but I don't see how to associate an xml layout file with the view (apart the primary res/layout/main.xml file, which provides the primary layout for the app.
How can I layout my custom views in XML?
Edit: My question was unclear. What I'm looking to do is associate a my_widget.xml file with my customized view. Then in my_widget.xml I'd like to define various TextViews, etc, and plug them into my View class.
Use the fully qualified name of your custom view class in place of one of the built-in views. Here's a layout, for instance, that fills the window with your class:
<?xml version="1.0" encoding="utf-8"?>
<my.package.MyCustomView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/my_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
To construct Views from XML, use LayoutInflater.
You can use findViewById (int id) with an id defined in XML. See the example in the android doc here (scroll down to IDs).
Is there a way to link inherit class to xml file.
I am trying to connect extended class to widget in the xml file.
Is it possible ?
Thanks in advance.
You must have noticed that all the nodes that we specify in the layout XMLs are actually either View classes(for e.g: TextView, EditView) or view containers/layout managers(e.g: LinearLayout, RelativeLayout etc.). Android allows you to create custom views and containers by extending the View class and one of the layout managers, respectively. You can then choose to inflate such views directly from code or specify them as nodes in your layout XMLs.
For instance, assuming you create a View class such as:
public class com.views.MyView extends View{}
then you can include this class directly in you layout XML by saying:
<LinearLayout ..>
<com.views.MyView .. />
</LinearLayout>
Note that when you specify your View class directly in XML there are a few important subtleties to consider such as:
When inflating the custom view, the framework will call different constructor of the view. The arguments would be a context object and AttributeSet(containing attributes you set in the XML).
For more details refer this