implement a slider for setting the widget background opacity

app/src/main/java/calculator/simplemobiletools/com/simple_calculator/Constants.java

@@ -24,4 +24,8 @@ public class Constants {
     public static final String SEVEN = "seven";
     public static final String EIGHT = "eight";
     public static final String NINE = "nine";
+
+    public static final String PREFS = "prefs";
+    public static final String VALUE = "value";
+    public static final String WIDGET_BG_COLOR = "widget_bg";
 }

app/src/main/java/calculator/simplemobiletools/com/simple_calculator/MyWidgetConfigure.java

@@ -2,18 +2,25 @@ package calculator.simplemobiletools.com.simple_calculator;
 
 import android.app.Activity;
 import android.appwidget.AppWidgetManager;
+import android.content.Context;
 import android.content.Intent;
+import android.content.SharedPreferences;
+import android.graphics.Color;
 import android.os.Bundle;
 import android.view.View;
-import android.widget.Button;
+import android.widget.RemoteViews;
+import android.widget.SeekBar;
 
 import butterknife.Bind;
 import butterknife.ButterKnife;
 import butterknife.OnClick;
 
-public class MyWidgetConfigure extends Activity {
+public class MyWidgetConfigure extends Activity implements SeekBar.OnSeekBarChangeListener {
-    @Bind(R.id.btn_reset) Button resetBtn;
+    @Bind(R.id.btn_reset) View resetBtn;
+    @Bind(R.id.config_seekbar) SeekBar seekBar;
+    @Bind(R.id.config_calc) View background;
     private int widgetId;
+    private int newBgColor;
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
@@ -22,11 +29,13 @@ public class MyWidgetConfigure extends Activity {
         ButterKnife.bind(this);
 
         resetBtn.setVisibility(View.VISIBLE);
+        seekBar.setOnSeekBarChangeListener(this);
+        seekBar.setProgress(50);
+
         final Intent intent = getIntent();
         final Bundle extras = intent.getExtras();
-        if (extras != null) {
+        if (extras != null)
             widgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetManager.INVALID_APPWIDGET_ID);
-        }
 
         if (widgetId == AppWidgetManager.INVALID_APPWIDGET_ID)
             finish();
@@ -36,9 +45,44 @@ public class MyWidgetConfigure extends Activity {
 
     @OnClick(R.id.config_save)
     public void saveConfig() {
+        final AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(this);
+        final RemoteViews views = new RemoteViews(getPackageName(), R.layout.activity_main);
+        views.setInt(R.id.calculator_holder, "setBackgroundColor", newBgColor);
+        appWidgetManager.updateAppWidget(widgetId, views);
+
+        storeWidgetBackground();
+        requestWidgetUpdate();
+
         final Intent resultValue = new Intent();
         resultValue.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, widgetId);
         setResult(RESULT_OK, resultValue);
         finish();
     }
+
+    private void storeWidgetBackground() {
+        final SharedPreferences prefs = getSharedPreferences(Constants.PREFS, Context.MODE_PRIVATE);
+        prefs.edit().putInt(Constants.WIDGET_BG_COLOR, newBgColor).apply();
+    }
+
+    private void requestWidgetUpdate() {
+        final Intent intent = new Intent(AppWidgetManager.ACTION_APPWIDGET_UPDATE, null, this, MyWidgetProvider.class);
+        intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS, new int[]{widgetId});
+        sendBroadcast(intent);
+    }
+
+    @Override
+    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
+        final float percent = (float) progress / (float) 100;
+        final int alpha = (int) (255 * percent);
+        newBgColor = Color.argb(alpha, 0, 0, 0);
+        background.setBackgroundColor(newBgColor);
+    }
+
+    @Override
+    public void onStartTrackingTouch(SeekBar seekBar) {
+    }
+
+    @Override
+    public void onStopTrackingTouch(SeekBar seekBar) {
+    }
 }

app/src/main/java/calculator/simplemobiletools/com/simple_calculator/MyWidgetProvider.java

@@ -11,9 +11,6 @@ import android.view.View;
 import android.widget.RemoteViews;
 
 public class MyWidgetProvider extends AppWidgetProvider implements Calculator {
-    private static final String PREFS = "prefs";
-    private static final String VALUE = "value";
-
     private static int[] widgetIds;
     private static RemoteViews remoteViews;
     private static CalculatorImpl calc;
@@ -61,19 +58,22 @@ public class MyWidgetProvider extends AppWidgetProvider implements Calculator {
     }
 
     private void initVariables(Context context) {
+        prefs = initPrefs(context);
         final ComponentName component = new ComponentName(context, MyWidgetProvider.class);
         remoteViews = new RemoteViews(context.getPackageName(), R.layout.activity_main);
         remoteViews.setViewVisibility(R.id.btn_reset, View.VISIBLE);
+        final int newBgColor = prefs.getInt(Constants.WIDGET_BG_COLOR, context.getResources().getColor(R.color.dark_grey));
+        remoteViews.setInt(R.id.calculator_holder, "setBackgroundColor", newBgColor);
+
         widgetManager = AppWidgetManager.getInstance(context);
         widgetIds = widgetManager.getAppWidgetIds(component);
 
-        prefs = initPrefs(context);
+        final String value = prefs.getString(Constants.VALUE, "0");
-        final String value = prefs.getString(VALUE, "0");
         calc = new CalculatorImpl(this, value);
     }
 
     private SharedPreferences initPrefs(Context context) {
-        return context.getSharedPreferences(PREFS, Context.MODE_PRIVATE);
+        return context.getSharedPreferences(Constants.PREFS, Context.MODE_PRIVATE);
     }
 
     @Override
@@ -109,7 +109,7 @@ public class MyWidgetProvider extends AppWidgetProvider implements Calculator {
     }
 
     private void myAction(String action, Context context) {
-        if (calc == null)
+        if (calc == null || remoteViews == null || widgetManager == null || widgetIds == null || prefs == null)
             initVariables(context);
 
         switch (action) {
@@ -173,7 +173,7 @@ public class MyWidgetProvider extends AppWidgetProvider implements Calculator {
     public void setValue(String value) {
         remoteViews.setTextViewText(R.id.result, value);
         widgetManager.updateAppWidget(widgetIds, remoteViews);
-        prefs.edit().putString(VALUE, value).apply();
+        prefs.edit().putString(Constants.VALUE, value).apply();
     }
 
     @Override
@@ -187,6 +187,6 @@ public class MyWidgetProvider extends AppWidgetProvider implements Calculator {
         if (prefs == null)
             prefs = initPrefs(context);
 
-        prefs.edit().remove(VALUE).apply();
+        prefs.edit().remove(Constants.VALUE).apply();
     }
 }

app/src/main/res/layout/widget_config.xml

@@ -34,5 +34,15 @@
             android:paddingRight="@dimen/activity_margin"
             android:text="Save"
             android:textSize="@dimen/config_text_size"/>
+
+        <SeekBar
+            android:id="@+id/config_seekbar"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_alignParentLeft="true"
+            android:layout_alignParentStart="true"
+            android:layout_centerVertical="true"
+            android:layout_marginRight="@dimen/activity_margin"
+            android:layout_toLeftOf="@id/config_save"/>
     </RelativeLayout>
 </RelativeLayout>

app/src/main/res/values/colors.xml

@@ -2,7 +2,7 @@
 <resources>
     <color name="colorPrimary">#3F51B5</color>
     <color name="colorPrimaryDark">#303F9F</color>
-    <color name="colorAccent">#FF4081</color>
+    <color name="colorAccent">#FF0000</color>
     <color name="dark_grey">#88000000</color>
     <color name="dark_grey_pressed">#22000000</color>
 </resources>