Changing Gradient Background Colors on Android at Runtime

Changing gradient background colors on Android at runtime

Yes! Found a way!

Had to forget about XML, but here's how I did it:

On my getView() overloaded function (ListAdapter) I just had to:

    int h = v.getHeight();
    ShapeDrawable mDrawable = new ShapeDrawable(new RectShape());
    mDrawable.getPaint().setShader(new LinearGradient(0, 0, 0, h, Color.parseColor("#330000FF"), Color.parseColor("#110000FF"), Shader.TileMode.REPEAT));
    v.setBackgroundDrawable(mDrawable);

And that gave me the same result as the XML background above. Now I can programmatically set the background color.

Change gradient center dynamically

You can achieve your goal by using Shader

ShapeDrawable.ShaderFactory sf = new ShapeDrawable.ShaderFactory() {
    @Override
    public Shader resize(int width, int height) {
        return new LinearGradient(width/2, 0, width/2, height,
                new int[]{0xff000000, 0xff42f448, 0xff000000},
                new float[]{0, 0.3f, 1},  // start, center and end position
                Shader.TileMode.CLAMP);
    }
};

PaintDrawable pd = new PaintDrawable();
pd.setShape(new RectShape());
pd.setShaderFactory(sf);

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
    layout.setBackground(pd);
} else
    layout.setBackgroundDrawable(pd);

Set the background colour of a Layout view to a gradient in Android?

create gradient.xml in /res/drawable:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
        android:startColor="#FFFFFF"
        android:endColor="#00000000"
        android:angle="45"/>    
</shape>

and in your main.xml layout file in /res/layout:

<?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"
    android:background="@drawable/gradient"
    >   
</LinearLayout>

you can specify the angle by replacing the android:angle value and start/end colour by replacing android:startColor and android:endColor

How do I programmatically set the background color gradient on a Custom Title Bar?

To do this in code, you create a GradientDrawable.

The only chance to set the angle and color is in the constructor.
If you want to change the color or angle, just create a new GradientDrawable and set it as the background

    View layout = findViewById(R.id.mainlayout);

    GradientDrawable gd = new GradientDrawable(
            GradientDrawable.Orientation.TOP_BOTTOM,
            new int[] {0xFF616261,0xFF131313});
    gd.setCornerRadius(0f);

    layout.setBackgroundDrawable(gd);

For this to work, I added an id to your main LinearLayout as follows

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/mainlayout"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
<ImageView   
              android:layout_width="fill_parent"
              android:layout_height="wrap_content"
              android:src="@drawable/title_bar_logo"
              android:gravity="center_horizontal"
              android:paddingTop="0dip"/>

</LinearLayout>

And to use this as for a custom title bar

    getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE,R.layout.custom_title_bar);
    View title = getWindow().findViewById(R.id.mainlayout);
    title.setBackgroundDrawable(gd);

Change background colour dynamically

Try creating three Views underneath the RangeSeekBar, and updating the widths of each as the sliders are moved.

Very roughly, this might look like:

<RelativeLayout android:layout_width="wrap_content" android:layout_height="wrap_content">
     <View
         android:id="@+id/green"
         android:layout_width="100dp"
         android:layout_height="match_parent"
         android:background="#00FF00"/>
     <View
         android:id="@+id/orange"
         android:layout_toRightOf="@id/green"
         android:layout_width="100dp"
         android:layout_height="match_parent"
         android:background="#FFFF00"/>
     <View
         android:id="@+id/red"
         android:layout_toRightOf="@id/orange"
         android:layout_width="100dp"
         android:layout_height="match_parent"
         android:background="#FF0000"/>
     <RangeSeekBar android:layout_width="300dp" android:layout_height="wrap_content">
</RelativeLayout>

In this example, you would update the widths of the three colour views so that they add up to 300dp, as the sliders are moved.

You can either use solid colours for the backgrounds of the three views, which would look like your second image, or create three gradients (green to green-yellow, yellow-orange, orange-red).

Gradient Background color in Java

Save the Gradient as an XML in your drawable.

<shape xmlns:android="http://schemas.android.com/apk/res/android" 
android:shape="rectangle" >
<gradient
android:angle="135"
android:centerColor="#16a085"
android:endColor="#2980b9"
android:startColor="#2980b9" />
</shape>

Replace

 ab.setBackgroundDrawable (new ColorDrawable(Color.parseColor(#2c3e50'))); 

with

ab.setBackgroundResource(R.drawable.color_gradient);

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