视图有minHeight,但不知何故缺少maxHeight:
我要实现的是有一些项目(视图)填充一个ScrollView。当有1..3个项目,我想直接显示他们。意思是ScrollView有1,2或3个项的高度。
当有4个或更多的项目时,我希望ScrollView停止展开(因此是maxHeight)并开始提供滚动。
然而,不幸的是,没有办法设置maxHeight。所以我可能需要通过编程方式将ScrollView的高度设置为WRAP_CONTENT当有1。当有4个或更多的项目时,设置高度为3*sizeOf(视图)。
有人能解释为什么没有maxHeight提供,当已经有一个minHeight?
(BTW:一些视图,如ImageView有一个maxHeight实现。)
这对我来说是有效的,使它在xml中可定制:
MaxHeightScrollView.java:
public class MaxHeightScrollView extends ScrollView {
private int maxHeight;
private final int defaultHeight = 200;
public MaxHeightScrollView(Context context) {
super(context);
}
public MaxHeightScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
if (!isInEditMode()) {
init(context, attrs);
}
}
public MaxHeightScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
if (!isInEditMode()) {
init(context, attrs);
}
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
public MaxHeightScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
if (!isInEditMode()) {
init(context, attrs);
}
}
private void init(Context context, AttributeSet attrs) {
if (attrs != null) {
TypedArray styledAttrs = context.obtainStyledAttributes(attrs, R.styleable.MaxHeightScrollView);
//200 is a defualt value
maxHeight = styledAttrs.getDimensionPixelSize(R.styleable.MaxHeightScrollView_maxHeight, defaultHeight);
styledAttrs.recycle();
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
heightMeasureSpec = MeasureSpec.makeMeasureSpec(maxHeight, MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
attr.xml
<declare-styleable name="MaxHeightScrollView">
<attr name="maxHeight" format="dimension" />
</declare-styleable>
示例布局
<blah.blah.MaxHeightScrollView android:layout_weight="1"
app:maxHeight="90dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<EditText android:id="@+id/commentField"
android:hint="Say Something"
android:background="#FFFFFF"
android:paddingLeft="8dp"
android:paddingRight="8dp"
android:gravity="center_vertical"
android:maxLines="500"
android:minHeight="36dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</blah.blah.MaxHeightScrollView>
MaxHeightScrollView自定义视图
public class MaxHeightScrollView extends ScrollView {
private int maxHeight;
public MaxHeightScrollView(Context context) {
this(context, null);
}
public MaxHeightScrollView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public MaxHeightScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context, attrs);
}
private void init(Context context, AttributeSet attrs) {
TypedArray styledAttrs =
context.obtainStyledAttributes(attrs, R.styleable.MaxHeightScrollView);
try {
maxHeight = styledAttrs.getDimensionPixelSize(R.styleable.MaxHeightScrollView_mhs_maxHeight, 0);
} finally {
styledAttrs.recycle();
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
if (maxHeight > 0) {
heightMeasureSpec = MeasureSpec.makeMeasureSpec(maxHeight, MeasureSpec.AT_MOST);
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
style.xml
<declare-styleable name="MaxHeightScrollView">
<attr name="mhs_maxHeight" format="dimension" />
</declare-styleable>
使用
<....MaxHeightScrollView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:mhs_maxHeight="100dp"
>
...
</....MaxHeightScrollView>