Android setLayerType 硬件加速问题

最新推荐文章于 2023-04-28 10:53:47 发布

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最新推荐文章于 2023-04-28 10:53:47 发布 · 1.3w 阅读

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#手机 #hierarchy #android #application #colors

本文详细介绍了Android系统中硬件加速的应用，从3.0版本开始支持硬件加速，可在Application、Activity、Window和View四个级别进行控制。硬件加速能提升性能，但也可能导致某些自定义View出现问题。开启硬件加速可能导致WebView性能下降，背景透明设置无效。Android的绘制模型分为基于软件和硬件两种，硬件加速模型通过记录和更新显示列表提高效率，减少了不必要的重绘操作。

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2014-3-3 补充：

在View的源码中有下面这样一段：

  /**
     * <p>Specifies the type of layer backing this view. The layer can be
     * {@link #LAYER_TYPE_NONE}, {@link #LAYER_TYPE_SOFTWARE} or
     * {@link #LAYER_TYPE_HARDWARE}.</p>
     *
     * <p>A layer is associated with an optional {@link android.graphics.Paint}
     * instance that controls how the layer is composed on screen. The following
     * properties of the paint are taken into account when composing the layer:</p>
     * <ul>
     * <li>{@link android.graphics.Paint#getAlpha() Translucency (alpha)}</li>
     * <li>{@link android.graphics.Paint#getXfermode() Blending mode}</li>
     * <li>{@link android.graphics.Paint#getColorFilter() Color filter}</li>
     * </ul>
     *
     * <p>If this view has an alpha value set to < 1.0 by calling
     * {@link #setAlpha(float)}, the alpha value of the layer's paint is superceded
     * by this view's alpha value.</p>
     *
     * <p>Refer to the documentation of {@link #LAYER_TYPE_NONE},
     * {@link #LAYER_TYPE_SOFTWARE} and {@link #LAYER_TYPE_HARDWARE}
     * for more information on when and how to use layers.</p>
     *
     * @param layerType The type of layer to use with this view, must be one of
     *        {@link #LAYER_TYPE_NONE}, {@link #LAYER_TYPE_SOFTWARE} or
     *        {@link #LAYER_TYPE_HARDWARE}
     * @param paint The paint used to compose the layer. This argument is optional
     *        and can be null. It is ignored when the layer type is
     *        {@link #LAYER_TYPE_NONE}
     *
     * @see #getLayerType()
     * @see #LAYER_TYPE_NONE
     * @see #LAYER_TYPE_SOFTWARE
     * @see #LAYER_TYPE_HARDWARE
     * @see #setAlpha(float)
     *
     * @attr ref android.R.styleable#View_layerType
     */
    public void setLayerType(int layerType, Paint paint) {
        if (layerType < LAYER_TYPE_NONE || layerType > LAYER_TYPE_HARDWARE) {
            throw new IllegalArgumentException("Layer type can only be one of: LAYER_TYPE_NONE, "
                    + "LAYER_TYPE_SOFTWARE or LAYER_TYPE_HARDWARE");
        }

        if (layerType == mLayerType) {
            if (layerType != LAYER_TYPE_NONE && paint != mLayerPaint) {
                mLayerPaint = paint == null ? new Paint() : paint;
                invalidateParentCaches();
                invalidate(true);
            }
            return;
        }

        // Destroy any previous software drawing cach