Create custom Android view/widget

Question

I'm attempting to create a custom widget which I can use in my activity's layout. I've created a class for the widget which extends View.

import android.app.Service;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;

import be.robinj.ubuntu.R;

public class AppLauncher extends View
{
    private String name;
    private String description;
    private boolean special;
    private AppIcon icon;
    private View view;

    public AppLauncher (Context context, AttributeSet attrs)
    {
        super (context, attrs);

        LayoutInflater inflater = (LayoutInflater) context.getSystemService (Service.LAYOUT_INFLATER_SERVICE);
        this.view = inflater.inflate (R.layout.widget_applauncher, null, false);

        TypedArray styleAttrs = context.getTheme ().obtainStyledAttributes (attrs, R.styleable.AppLauncher, 0, 0);
        this.name = styleAttrs.getString (R.styleable.AppLauncher_label);
        this.description = styleAttrs.getString (R.styleable.AppLauncher_description);
        this.special = styleAttrs.getBoolean (R.styleable.AppLauncher_special, false);
        this.icon = new AppIcon (styleAttrs.getDrawable (R.styleable.AppLauncher_icon));
    }

    ...
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="64dp"
              android:layout_height="64dp">

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="#ffff9243"
        android:layout_margin="6dp">

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="@drawable/launcher_icon_bg">

            <ImageView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/imgIcon"
                android:src="@drawable/ic_launcher" />
        </LinearLayout>
    </LinearLayout>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="AppLauncher">
        <attr name="label" format="string" />
        <attr name="description" format="string" />
        <attr name="icon" format="integer" />
        <attr name="special" format="boolean" />
    </declare-styleable>
</resources>

That's all fine, but the Java code is only going to contain the logic part, preferably. ~~What I can't figure out is how I can specify which layout XML file should be used for my custom view/widget.~~ Inflating the layout presumably loads it. The inflate () methods require a second and third parameter, though. Every example I can find shows this being passed as the second parameter, but the second parameter should be a ViewGroup, while this extends View. Where do I magically get this required ViewGroup object from? Passing null and false does not throw an error, but neither does it do anything else (nothing shows up when I run the app).

Pr38y · Accepted Answer · 2014-08-20 12:50:33Z

1

Use the following code to inflate xml in a custom view

    public AppLauncher (Context context, AttributeSet attrs)
    {
             super (context, attrs);
             LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Service.LAYOUT_INFLATER_SERVICE);
             View parent = inflater.inflate(R.layout.home_activity, this);
    }

answered Aug 20, 2014 at 12:50

Pr38y

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4 Comments

Pr38y Over a year ago

ctrl+shift+o import your R file.

RobinJ Over a year ago

I thought Import Class would result in importing android.R and that somehow my own R.java file had faield to compile. I should have checked. Sorry, and thanks :)

RobinJ Over a year ago

This answer is incorrect. this is not a valid parameter, since this is a View while a ViewGroup is expected. So where am I supposed to get this ViewGroup from?

Pr38y Over a year ago

extend ViewGroup class not View as you already figured out.

eldjon · Accepted Answer · 2014-08-20 23:10:47Z

1

It seems from your source code that you want to create a ViewGroup therefore you need to extend the appropriate class LinearLayout for example. Next you can create an xml file as usual and inflate it in your custom ViewGroup constructor:

 LayoutInflater inflater = (LayoutInflater) context
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    inflater.inflate(R.layout.ur_view, this);

You may then inject your custom view within any layout in the following way:

<package.def.AppLauncher .../>

or:

<View 
      class="package.defAppLauncher"
/View>

edited Aug 20, 2014 at 23:10

answered Aug 20, 2014 at 12:58

eldjon

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4 Comments

RobinJ Over a year ago

I'm a bit unclear as to what the second parameter is, since this is not working (because it refers to my AppLauncher class). According to the docs it should be a ViewGroup, which doesn't really tell me a whole lot.

RobinJ Over a year ago

When I add the view/widget to my layout it's just empty/invisible, so something's not right.

RobinJ Over a year ago

This answer is incorrect. Passing null as a parameter will not add the view to its parent, causing it to not show up.

eldjon Over a year ago

if you extend a ViewGroup like LinearLayout that would solve ur problem

RobinJ · Accepted Answer · 2014-08-20 18:30:03Z

0

Thanks to Pr38y and eldjon for LayoutInflater.
In the end the big problem was that I needed to extend LinearLayout rather than View.

answered Aug 20, 2014 at 18:30

RobinJ

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