Increase Android Gradient Center Scalability

Question

I created an Android gradient drawable where the top and bottom are black and the center is transparent:

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <gradient
        android:startColor="@android:color/black"
        android:centerColor="@android:color/transparent"
        android:endColor="@android:color/black"
        android:angle="90"/>
</shape>

The resulting gradient is as follows:

As you can see, the black parts extend to most of the screen. I want the black to appear only on a small part above and below. Is there a way to make the transparent center larger or reduce the upper and lower black bars?

I tried playing around with some of the other XML attributes mentioned in the related documentation GradientDrawable, but none of them seem to do or differ.

Answer 1

XML layer-list gradient.

gradient centerY centerColor . centerY 0.9 0.1, 10% .

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <gradient
                android:angle="90"
                android:centerColor="@android:color/transparent"
                android:centerY="0.9"
                android:endColor="@android:color/black"
                android:startColor="@android:color/transparent" />
        </shape>
    </item>

    <item>
        <shape>
            <gradient
                android:angle="90"
                android:centerColor="@android:color/transparent"
                android:centerY="0.1"
                android:endColor="@android:color/transparent"
                android:startColor="@android:color/black" />
        </shape>
    </item>
</layer-list>

---

API 23 , android:height. , , , .

, 60sp, android:gravity .

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:height="60sp"
        android:gravity="top">
        <shape android:shape="rectangle">
            <gradient
                android:angle="90"
                android:endColor="@android:color/black"
                android:startColor="@android:color/transparent" />
        </shape>
    </item>
    <item
        android:height="65sp"
        android:gravity="bottom">
        <shape android:shape="rectangle">
            <gradient
                android:angle="90"
                android:endColor="@android:color/transparent"
                android:startColor="@android:color/black" />
        </shape>
    </item>
</layer-list>

---

@Luksprog @thenaoh .

, , XML. , , @lelloman, .

Answer 2

Drawable. LinearGradient , view.setBackground(new CustomDrawable());.

public class CustomDrawable extends Drawable {

    private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private int[] colors;
    private float[] positions;

    public CustomDrawable() {
        paint.setStyle(Paint.Style.FILL);
        this.colors = new int[]{0xff000000, 0xffaaaaaa, 0xffffffff, 0xffaaaaaa, 0xff000000};
        this.positions = new float[]{.0f, .2f, .5f, .8f, 1.f};
    }

    @Override
    public void setBounds(int left, int top, int right, int bottom) {
        super.setBounds(left, top, right, bottom);    

        LinearGradient linearGradient = new LinearGradient(left, top,left, bottom, colors, positions, Shader.TileMode.CLAMP);
        paint.setShader(linearGradient);
    }

    @Override
    public void draw(@NonNull Canvas canvas) {    
        canvas.drawRect(getBounds(), paint);
    }

    @Override
    public void setAlpha(@IntRange(from = 0, to = 255) int alpha) {
        paint.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(@Nullable ColorFilter colorFilter) {
        paint.setColorFilter(colorFilter);
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSPARENT;
    }
}

Answer 3

, , ( 60dp):

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item
    android:bottom="40dp">
    <shape android:shape="rectangle">
        <gradient
            android:type="linear"
            android:angle="90"
            android:startColor="#FFFFFF"
            android:endColor="#000000"/>
    </shape>
</item>
<item
    android:top="20dp"
    android:bottom="20dp"
    android:gravity="center_vertical">
    <shape android:shape="rectangle">
        <solid android:color="#FFFFFF"/>
    </shape>
</item>
<item
    android:top="40dp"
    android:gravity="bottom">
    <shape android:shape="rectangle">
        <gradient
            android:type="linear"
            android:angle="90"
            android:startColor="#000000"
            android:endColor="#FFFFFF"/>
    </shape>
</item>
</layer-list>

, , :

public class MyView extends ImageView
{
    private Paint paint = null;

    public MyView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);
        paint.setShader(getLinearGradient(0, getHeight()));
        canvas.drawPaint(paint);
    }

    private LinearGradient getLinearGradient(float y0, float y1)
    {
        // colors :
        int[] listeColors = new int[3];
        listeColors[0] = 0xFF000000;
        listeColors[1] = 0xFFFFFFFF;
        listeColors[2] = 0xFFFFFFFF;

        // positions :
        float[] listPositions = new float[3];
        listPositions[0] = 0;
        listPositions[1] = 0.25F;
        listPositions[2] = 1;

        // gradient :
        return new LinearGradient(0, y0, 0, y0 + (y1 - y0) / 2, listeColors, listPositions, Shader.TileMode.MIRROR);
    }
}

Hope this helps.