Part 1 – Simple Home Screen Widget

[embedyt] https://www.youtube.com/watch?v=xGQJg31TPtU[/embedyt]

In this tutorial we will learn, how to create a simple home screen app widget that contains a button and opens the MainActivity when we click it.
For this we will create a widget layout, an AppWidgetProvider class and an AppWidgetProviderInfo xml file. In the AppWidgetProvider java file we will then override onUpdate and create a PendingIntent which brings us to our MainActivity. We set this intent on our widget button with help of the RemoteViews class and then update our widget with the appWidgetManager object. We repeat this process for all instances of our widget by looping through the appWidgetIds int array.
In the app widget info xml file, we define the update frequency with updatePeriodMillis, the widgetCategory, minHeight, minWidth, minResizeWidth, initialLayout and more.
Lastly we register our AppWidgetProvider in the AndroidManifest.xml file as a broadcast receiver with the APPWIDGET_UPDATE intent filter. We register our appwidget info object in the meta data tag with android.appwidget.provider.
Our widget will have a previewImage which we create with help of the Widget Preview app and it will be resizable.

App Widget Guidelines:
developer.android.com/guide/topics/appwidgets/index.html
developer.android.com/guide/practices/ui_guidelines/widget_design.html

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example_widget.xmlExampleAppWidgetProvider.javaexample_appwidget_info.xmlAndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/example_widget_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Press me" />

</RelativeLayout>

package com.codinginflow.widgetexample;

import android.app.PendingIntent;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.Context;
import android.content.Intent;
import android.widget.RemoteViews;


public class ExampleAppWidgetProvider extends AppWidgetProvider {

    @Override
    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
        for (int appWidgetId : appWidgetIds) {
            Intent intent = new Intent(context, MainActivity.class);
            PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);

            RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.example_widget);
            views.setOnClickPendingIntent(R.id.example_widget_button, pendingIntent);

            appWidgetManager.updateAppWidget(appWidgetId, views);
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
    android:initialLayout="@layout/example_widget"
    android:minHeight="40dp"
    android:minResizeWidth="40dp"
    android:minWidth="110dp"
    android:previewImage="@drawable/widget_preview"
    android:resizeMode="vertical|horizontal"
    android:updatePeriodMillis="3600000"
    android:widgetCategory="home_screen">

</appwidget-provider>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.codinginflow.widgetexample">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:launchMode="singleTop">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver android:name=".ExampleAppWidgetProvider">
            <intent-filter>
                <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
            </intent-filter>
            <meta-data
                android:name="android.appwidget.provider"
                android:resource="@xml/example_appwidget_info" />
        </receiver>
    </application>

</manifest>