通过onMeasure方法修改布局高跟宽的比例

试用于轮播图的屏幕宽跟高的固定比例

自己定义布局继承重写onMeasure方法

<com.sanwn.ddmb.view.AppBarLayoutView
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:ratio="2">

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

重写类是实例

public class AppBarLayoutView extends AppBarLayout {

private static final String TAG = "RatioLayout";
// 宽和高的比例
private float ratio = 0.0f;

public AppBarLayoutView(Context context) {
super(context);
}

public AppBarLayoutView(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RatioLayout);
ratio = a.getFloat(R.styleable.RatioLayout_ratio, 0.0f);
a.recycle();
}

public void setRatio(float f) {
ratio = f;
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int width = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight();
int height = MeasureSpec.getSize(heightMeasureSpec) - getPaddingTop() - getPaddingBottom();
if (widthMode == MeasureSpec.EXACTLY && heightMode != MeasureSpec.EXACTLY && ratio != 0.0f) {
height = (int) (width / ratio + 0.5f);
heightMeasureSpec = MeasureSpec.makeMeasureSpec(height + getPaddingTop() + getPaddingBottom(),
MeasureSpec.EXACTLY);
} else if (widthMode != MeasureSpec.EXACTLY && heightMode == MeasureSpec.EXACTLY && ratio != 0.0f) {
width = (int) (height * ratio + 0.5f);
widthMeasureSpec = MeasureSpec.makeMeasureSpec(width + getPaddingLeft() + getPaddingRight(),
MeasureSpec.EXACTLY);
}
Log.d(TAG, "onMeasure: ==="+height+"==="+width);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}