在视图上叠加颜色

Question

对于自定义AdapterView实现,我想为所选项添加颜色叠加.如何为AdapterView的子项添加颜色叠加？

Answer 1

如果您使用自己的布局,只需将容器更改为RelativeLayout(或继承自的Layout类RelativeLayout),并将颜色叠加层放在主布局之后.您只需要添加一个View并设置它的背景和alpha.alpha设置为值1将激活此叠加,而设置alpha为0将恢复正常.

例:

<RelativeLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent">

  <!-- add your views here -->

  <View
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#8000FF00" />

</RelativeLayout>

这将覆盖具有50%alpha的绿色图层,而不是布局中位于其之前的其他视图.

Answer 2

好的,我做了一些更多的研究.这就是我最终提出的:

// prepare a gray filter setting saturation to 0, or ...
ColorMatrix cm = new ColorMatrix();
cm.setSaturation(0);
Paint paint = new Paint();
ColorFilter filter = new ColorMatrixColorFilter(cm);

// ... prepare a color filter
ColorFilter filter = new PorterDuffColorFilter(Color.rgb(34, 136, 201), PorterDuff.Mode.OVERLAY);

// create paint
paint.setColorFilter(filter);


// override dispatchDraw of the view
@Override
protected void dispatchDraw(Canvas canvas) {
    if (isPressed()) {
        canvas.saveLayer(null, paint, Canvas.ALL_SAVE_FLAG);
        super.dispatchDraw(canvas);
        canvas.restore();
    } else {
        super.dispatchDraw(canvas);
    }
}