android.view.View#resolveSizeAndState ( )源码实例Demo

/**
 * Set this FlexboxLayouts' width and height depending on the calculated size of main axis and
 * cross axis.
 *
 * @param flexDirection     the value of the flex direction
 * @param widthMeasureSpec  horizontal space requirements as imposed by the parent
 * @param heightMeasureSpec vertical space requirements as imposed by the parent
 * @param childState        the child state of the View
 * @see #getFlexDirection()
 * @see #setFlexDirection(int)
 */
private void setMeasuredDimensionForFlex(@FlexDirection int flexDirection, int widthMeasureSpec,
                                         int heightMeasureSpec, int childState) {
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int widthSize = MeasureSpec.getSize(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    int heightSize = MeasureSpec.getSize(heightMeasureSpec);
    int calculatedMaxHeight;
    int calculatedMaxWidth;
    switch (flexDirection) {
        case FlexDirection.ROW: // Intentional fall through
        case FlexDirection.ROW_REVERSE:
            calculatedMaxHeight = getSumOfCrossSize() + getPaddingTop()
                    + getPaddingBottom();
            calculatedMaxWidth = getLargestMainSize();
            break;
        case FlexDirection.COLUMN: // Intentional fall through
        case FlexDirection.COLUMN_REVERSE:
            calculatedMaxHeight = getLargestMainSize();
            calculatedMaxWidth = getSumOfCrossSize() + getPaddingLeft() + getPaddingRight();
            break;
        default:
            throw new IllegalArgumentException("Invalid flex direction: " + flexDirection);
    }

    int widthSizeAndState;
    switch (widthMode) {
        case MeasureSpec.EXACTLY:
            if (widthSize < calculatedMaxWidth) {
                childState = View
                        .combineMeasuredStates(childState, View.MEASURED_STATE_TOO_SMALL);
            }
            widthSizeAndState = View.resolveSizeAndState(widthSize, widthMeasureSpec,
                    childState);
            break;
        case MeasureSpec.AT_MOST: {
            if (widthSize < calculatedMaxWidth) {
                childState = View
                        .combineMeasuredStates(childState, View.MEASURED_STATE_TOO_SMALL);
            } else {
                widthSize = calculatedMaxWidth;
            }
            widthSizeAndState = View.resolveSizeAndState(widthSize, widthMeasureSpec,
                    childState);
            break;
        }
        case MeasureSpec.UNSPECIFIED: {
            widthSizeAndState = View
                    .resolveSizeAndState(calculatedMaxWidth, widthMeasureSpec, childState);
            break;
        }
        default:
            throw new IllegalStateException("Unknown width mode is set: " + widthMode);
    }
    int heightSizeAndState;
    switch (heightMode) {
        case MeasureSpec.EXACTLY:
            if (heightSize < calculatedMaxHeight) {
                childState = View.combineMeasuredStates(childState,
                        View.MEASURED_STATE_TOO_SMALL
                                >> View.MEASURED_HEIGHT_STATE_SHIFT);
            }
            heightSizeAndState = View.resolveSizeAndState(heightSize, heightMeasureSpec,
                    childState);
            break;
        case MeasureSpec.AT_MOST: {
            if (heightSize < calculatedMaxHeight) {
                childState = View.combineMeasuredStates(childState,
                        View.MEASURED_STATE_TOO_SMALL
                                >> View.MEASURED_HEIGHT_STATE_SHIFT);
            } else {
                heightSize = calculatedMaxHeight;
            }
            heightSizeAndState = View.resolveSizeAndState(heightSize, heightMeasureSpec,
                    childState);
            break;
        }
        case MeasureSpec.UNSPECIFIED: {
            heightSizeAndState = View.resolveSizeAndState(calculatedMaxHeight,
                    heightMeasureSpec, childState);
            break;
        }
        default:
            throw new IllegalStateException("Unknown height mode is set: " + heightMode);
    }
    setMeasuredDimension(widthSizeAndState, heightSizeAndState);
}
 

@Override
public int resolveSizeAndState(int size, int measureSpec, int state) {
    return View.resolveSizeAndState(size, measureSpec, state);
}
 

public static int resolveSizeAndState(int size, int measureSpec, int childMeasuredState) {
    return View.resolveSizeAndState(size, measureSpec, childMeasuredState);
}
 

public static int resolveSizeAndState(int size, int measureSpec, int childMeasuredState) {
    return View.resolveSizeAndState(size, measureSpec, childMeasuredState);
}
 

public static int resolveSizeAndState(int size, int measureSpec, int childMeasuredState) {
    return View.resolveSizeAndState(size, measureSpec, childMeasuredState);
}
 

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);

    // General goal: Adjust dimensions to maintain the requested aspect ratio as much
    // as possible. Depending on the measure specs handed down, this may not be possible

    // Only set one of these to true
    boolean scaleWidth = false;
    boolean scaleHeight = false;

    // Sort out which dimension to scale, if either can be. There are 9 combinations of
    // possible measure specs; a few cases below handle multiple combinations
    //noinspection StatementWithEmptyBody
    if (widthMode == MeasureSpec.EXACTLY && heightMode == MeasureSpec.EXACTLY) {
        // Can't adjust sizes at all, do nothing
    } else if (widthMode == MeasureSpec.EXACTLY) {
        // Width is fixed, heightMode either AT_MOST or UNSPECIFIED, so adjust height
        scaleHeight = true;
    } else if (heightMode == MeasureSpec.EXACTLY) {
        // Height is fixed, widthMode either AT_MOST or UNSPECIFIED, so adjust width
        scaleWidth = true;
    } else if (widthMode == MeasureSpec.AT_MOST && heightMode == MeasureSpec.AT_MOST) {
        // Need to fit into box <= [width, height] in size.
        // Maximize the View's area while maintaining aspect ratio
        // This means keeping one dimension as large as possible and shrinking the other
        float boxAspectRatio = width / (float) height;
        if (boxAspectRatio > mAspectRatio) {
            // Box is wider than requested aspect; pillarbox
            scaleWidth = true;
        } else {
            // Box is narrower than requested aspect; letterbox
            scaleHeight = true;
        }
    } else if (widthMode == MeasureSpec.AT_MOST) {
        // Maximize width, heightSpec is UNSPECIFIED
        scaleHeight = true;
    } else if (heightMode == MeasureSpec.AT_MOST) {
        // Maximize height, widthSpec is UNSPECIFIED
        scaleWidth = true;
    } else {
        // Both MeasureSpecs are UNSPECIFIED. This is probably a pathological layout,
        // with width == height == 0
        // but arbitrarily scale height anyway
        scaleHeight = true;
    }

    // Do the scaling
    if (scaleWidth) {
        width = (int) (height * mAspectRatio);
    } else if (scaleHeight) {
        height = (int) (width / mAspectRatio);
    }

    // Override width/height if needed for EXACTLY and AT_MOST specs
    width = View.resolveSizeAndState(width, widthMeasureSpec, 0);
    height = View.resolveSizeAndState(height, heightMeasureSpec, 0);

    // Finally set the calculated dimensions
    setMeasuredDimension(width, height);
}
 

public static int resolveSizeAndState(int size, int measureSpec, int childMeasuredState) {
    return View.resolveSizeAndState(size, measureSpec, childMeasuredState);
}