这是一个可能的实现，它还支持检查布局。
几乎相同的解决方案可以应用于您希望的任何布局视图（只有 CTOR 不同）。
public class CheckableLinearLayout extends LinearLayout implements Checkable {
private boolean mChecked;
private static final String TAG = CheckableLinearLayout.class.getCanonicalName();
private static final int[] CHECKED_STATE_SET = { android.R.attr.state_checked };
private Drawable mForeground;
public CheckableLinearLayout(final Context context) {
this(context, null, 0);
}
public CheckableLinearLayout(final Context context, final AttributeSet attrs) {
this(context, attrs, 0);
}
public CheckableLinearLayout(final Context context, final AttributeSet attrs, final int defStyle) {
super(context, attrs, defStyle);
final TypedArray a = context
.obtainStyledAttributes(attrs, R.styleable.CheckableLinearLayout, defStyle, 0);
setForegroundEx(a.getDrawable(R.styleable.CheckableLinearLayout_foreground));
a.recycle();
}
public void setForegroundEx(final Drawable drawable) {
this.mForeground = drawable;
}
@Override
protected int[] onCreateDrawableState(final int extraSpace) {
final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);
if (isChecked()) {
mergeDrawableStates(drawableState, CHECKED_STATE_SET);
}
return drawableState;
}
@Override
protected void drawableStateChanged() {
super.drawableStateChanged();
final Drawable drawable = getBackground();
boolean needRedraw = false;
final int[] myDrawableState = getDrawableState();
if (drawable != null) {
drawable.setState(myDrawableState);
needRedraw = true;
}
if (mForeground != null) {
mForeground.setState(myDrawableState);
needRedraw = true;
}
if (needRedraw)
invalidate();
}
@Override
protected void onSizeChanged(final int width, final int height, final int oldwidth, final int oldheight) {
super.onSizeChanged(width, height, oldwidth, oldheight);
if (mForeground != null)
mForeground.setBounds(0, 0, width, height);
}
@Override
protected void dispatchDraw(final Canvas canvas) {
super.dispatchDraw(canvas);
if (mForeground != null)
mForeground.draw(canvas);
}
@Override
public boolean isChecked() {
return mChecked;
}
@Override
public void setChecked(final boolean checked) {
mChecked = checked;
refreshDrawableState();
//TODO think if you wish to also check inner views, maybe even recursively
}
@Override
public void toggle() {
setChecked(!mChecked);
}
@Override
public Parcelable onSaveInstanceState() {
// Force our ancestor class to save its state
final Parcelable superState = super.onSaveInstanceState();
final SavedState savedState = new SavedState(superState);
savedState.checked = isChecked();
return savedState;
}
@Override
public void onRestoreInstanceState(final Parcelable state) {
final SavedState savedState = (SavedState) state;
super.onRestoreInstanceState(savedState.getSuperState());
setChecked(savedState.checked);
requestLayout();
}
@SuppressLint("ClickableViewAccessibility")
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
@Override
public boolean onTouchEvent(final MotionEvent e) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && //
e.getActionMasked() == MotionEvent.ACTION_DOWN && //
mForeground != null)
mForeground.setHotspot(e.getX(), e.getY());
return super.onTouchEvent(e);
}
// /////////////
// SavedState //
// /////////////
private static class SavedState extends BaseSavedState {
boolean checked;
SavedState(final Parcelable superState) {
super(superState);
}
private SavedState(final Parcel in) {
super(in);
checked = (Boolean) in.readValue(null);
}
@Override
public void writeToParcel(final Parcel out, final int flags) {
super.writeToParcel(out, flags);
out.writeValue(checked);
}
@Override
public String toString() {
return TAG + ".SavedState{" + Integer.toHexString(System.identityHashCode(this)) + " checked=" + checked
+ "}";
}
@SuppressWarnings("unused")
public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
@Override
public SavedState createFromParcel(final Parcel in) {
return new SavedState(in);
}
@Override
public SavedState[] newArray(final int size) {
return new SavedState[size];
}
};
}
}
attr.xml
<declare-styleable name="CheckableLinearLayout">
<attr name="foreground"/>
</declare-styleable>
这是一种更简单的方法，使用 Kotlin，并且没有可检查的部分：
class LinearLayoutEx @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : LinearLayout(context, attrs, defStyle) {
var foregroundDrawable: Drawable? = null
set(value) {
field = value
invalidate()
}
init {
val a = context
.obtainStyledAttributes(attrs, R.styleable.LinearLayoutEx, defStyle, 0)
foregroundDrawable = a.getDrawable(R.styleable.LinearLayoutEx_foreground)
a.recycle()
}
override fun drawableStateChanged() {
super.drawableStateChanged()
val drawable = background
var needRedraw = false
val myDrawableState = drawableState
if (drawable != null) {
drawable.state = myDrawableState
needRedraw = true
}
if (foregroundDrawable != null) {
foregroundDrawable!!.state = myDrawableState
needRedraw = true
}
if (needRedraw)
invalidate()
}
override fun onSizeChanged(width: Int, height: Int, oldwidth: Int, oldheight: Int) {
super.onSizeChanged(width, height, oldwidth, oldheight)
foregroundDrawable?.setBounds(0, 0, width, height)
}
override fun dispatchDraw(canvas: Canvas) {
super.dispatchDraw(canvas)
foregroundDrawable?.draw(canvas)
}
@SuppressLint("ClickableViewAccessibility")
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
override fun onTouchEvent(e: MotionEvent): Boolean {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && e.actionMasked == MotionEvent.ACTION_DOWN)
foregroundDrawable?.setHotspot(e.x, e.y)
return super.onTouchEvent(e)
}
}
attr.xml
<declare-styleable name="LinearLayoutEx" tools:ignore="MissingDefaultResource">
<attr name="foreground"/>
</declare-styleable>