I'm trying to apply a linear gradient to my ListView. This is the content of my drawable xml:
<?xml versi开发者_如何学Pythonon="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<gradient
android:startColor="#3A3C39"
android:endColor="#181818"
android:angle="270"
/>
<corners android:radius="0dp" />
</shape>
So I apply it to my ListView with:
android:background="@drawable/shape_background_grey"
It works but it looks very "banded" on emulator and on a real device too.
Is there any way to reduce this "behaviour"?
As Romain Guy suggests:
listView.getBackground().setDither(true);
solves my problem
If this is not enough especially for AMOLED and/or hdpi devices try this:
@Override
public void onAttachedToWindow() {
super.onAttachedToWindow();
Window window = getWindow();
window.setFormat(PixelFormat.RGBA_8888);
}
You can simply enable dithering on your Drawable object.
Put this in your Activity:
@Override
public void onAttachedToWindow() {
super.onAttachedToWindow();
Window window = getWindow();
window.setFormat(PixelFormat.RGBA_8888);
}
If the dither and RGBA_888 setting don't help on some phones, the solution can be to set the element layerType
to software
, to disable the hardware acceleration
android:layerType="software"
This fixed my problem on a Samsung S5 phone.
For me on HTC Desire works like this
window.getDecorView().getBackground().setDither(true);
For me the banding disappeared when I set the android:useLevel="true" on the gradient: gradient_dark.xml
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient android:startColor="#464646"
android:endColor="#323232"
android:angle="270"
android:type="linear"
android:useLevel="true"
/>
</shape>
But first I tried using a Layer-List with a "noise" drawable to remove the banding, it helps but there is still some banding.
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
<item android:drawable="@drawable/gradient_dark"/>
<item>
<bitmap
android:gravity="center"
android:src="@drawable/noise_repeater"
android:tileMode="repeat" />
</item>
</layer-list>
The "noise_repeater" drawable i created and used
The only thing that worked for me was to set a slightly-transparent alpha channel on both the startColor and endColor.
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<gradient
android:startColor="#FE3A3C39"
android:endColor="#FE181818"
android:angle="270"
/>
</shape>
I got the idea to try this from this other SO question: android:dither=“true” does not dither, what's wrong?
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