自定义控件-平铺图片

使图片平铺背景

在这里使用自定义控件为了使图片能够铺平整个控件背景。

首先在样式里定义控件和属性

style：

<declare-styleable name="RatioLayout">
    <attr name="ratio" format="float"/>
</declare-styleable>

xml：

<com.example.photo.custom.RatioLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:ratio="1">

    <ImageView
        android:id="@+id/module_layout_welcome_iv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:contentDescription="@string/activity_welcome_iv" />
</com.example.photo.custom.RatioLayout>

java：

public class RatioLayout extends FrameLayout {

    private float ratio;

    public RatioLayout(@NonNull Context context) {
        super(context);
    }

    public RatioLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        /*获取自定义控件的属性集合*/
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.RatioLayout);
        /*根据id，获取属性值RatioLayout_ratio系统默认控件名_属性名*/
        ratio = typedArray.getFloat(R.styleable.RatioLayout_ratio, 0);
        /*回收*/
        typedArray.recycle();
    }

    public RatioLayout(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        /*获取模式*/
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        /*获取大小*/
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);

        /*MeasureSpec.AT_MOST 类似match_parent
         * MeasureSpec.EXACTLY 类似wrap_content
         * MeasureSpec.UNSPECIFIED 未定义*/

        if (widthMode == MeasureSpec.EXACTLY && heightMode != MeasureSpec.EXACTLY && ratio > 0) {
            /*根据布局推算出图片宽度*/
            int imageWidth=widthSize-getPaddingEnd()-getPaddingStart();
            /*根据图片宽度，宽高比，推算出图片高度*/
            int imageHeight= (int) (imageWidth/ratio+0.5f);
            /*根据图片高度算出控件高度*/
            heightSize=imageHeight+getPaddingTop()+getPaddingBottom();
            /*重新定义*/
            heightMeasureSpec= MeasureSpec.makeMeasureSpec(heightSize, MeasureSpec.EXACTLY);
        }

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
}