自定义EditText修改Compound Drawable触发无限Focus Change Event问题求助

嘿，这个问题我之前做自定义输入控件时也踩过坑！核心原因就是你在OnFocusChangeListener里修改CompoundDrawable时，系统会触发额外的焦点变更回调——这是因为修改Drawable会触发View的刷新/重布局逻辑，间接导致焦点状态被误判，进而形成无限循环。下面给你几个靠谱的解决思路：

方案1：添加标志位拦截重复回调 #

这是最直接的解决办法，用一个布尔变量标记当前是否正在主动更新Drawable，避免处理因修改Drawable引发的虚假焦点变更。

public class ClearableEditText extends EditText {
    private boolean isUpdatingDrawable = false;
    private Drawable clearDrawable;

    public ClearableEditText(Context context) {
        super(context);
        init();
    }

    // 别忘了实现其他构造方法（带AttributeSet、defStyleAttr的版本）

    private void init() {
        clearDrawable = getResources().getDrawable(R.drawable.ic_clear);
        clearDrawable.setBounds(0, 0, clearDrawable.getIntrinsicWidth(), clearDrawable.getIntrinsicHeight());
        
        setOnFocusChangeListener((v, hasFocus) -> {
            // 如果正在更新Drawable，直接跳过本次回调
            if (isUpdatingDrawable) {
                return;
            }
            updateClearIconVisibility(hasFocus);
        });

        // 处理清除图标的点击逻辑
        setOnTouchListener((v, event) -> {
            if (getCompoundDrawables()[2] != null) {
                boolean isClearIconClicked = event.getX() > (getWidth() - getPaddingRight() - clearDrawable.getIntrinsicWidth());
                if (isClearIconClicked && event.getAction() == MotionEvent.ACTION_UP) {
                    setText("");
                    return true;
                }
            }
            return false;
        });
    }

    private void updateClearIconVisibility(boolean hasFocus) {
        isUpdatingDrawable = true; // 开启标记
        if (hasFocus && !TextUtils.isEmpty(getText())) {
            setCompoundDrawables(getCompoundDrawables()[0], getCompoundDrawables()[1], clearDrawable, getCompoundDrawables()[3]);
        } else {
            setCompoundDrawables(getCompoundDrawables()[0], getCompoundDrawables()[1], null, getCompoundDrawables()[3]);
        }
        isUpdatingDrawable = false; // 关闭标记
    }
}

这个标志位就像一个“临时开关”，告诉系统：现在是我主动修改Drawable，这时候触发的焦点变化是假的，不用处理，直接切断无限循环的链条。

方案2：仅在必要时更新Drawable #

另一种思路是减少不必要的setCompoundDrawables调用——只有当当前Drawable状态和预期不符时，才去修改它，从根源上避免触发额外的焦点回调。

@Override
protected void onFocusChanged(boolean gainFocus, int direction, Rect previouslyFocusedRect) {
    boolean shouldShowIcon = gainFocus && !TextUtils.isEmpty(getText());
    Drawable currentRightDrawable = getCompoundDrawables()[2];

    // 只有当状态需要变更时，才更新Drawable
    if (shouldShowIcon && currentRightDrawable != clearDrawable) {
        setCompoundDrawables(getCompoundDrawables()[0], getCompoundDrawables()[1], clearDrawable, getCompoundDrawables()[3]);
    } else if (!shouldShowIcon && currentRightDrawable != null) {
        setCompoundDrawables(getCompoundDrawables()[0], getCompoundDrawables()[1], null, getCompoundDrawables()[3]);
    }

    // 必须调用父类方法，保证正常的焦点逻辑
    super.onFocusChanged(gainFocus, direction, previouslyFocusedRect);
}

这里我们重写了View自身的onFocusChanged方法，先判断当前是否需要显示图标，再对比现有Drawable的状态，只有不一致时才执行修改操作，避免了无意义的刷新。

方案3：结合TextWatcher优化状态判断 #

因为图标显示既依赖焦点状态，也依赖文本内容，我们可以把焦点变化和文本变化的逻辑合并，进一步减少不必要的更新：

private void init() {
    clearDrawable = getResources().getDrawable(R.drawable.ic_clear);
    clearDrawable.setBounds(0, 0, clearDrawable.getIntrinsicWidth(), clearDrawable.getIntrinsicHeight());

    // 监听文本变化
    addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            updateClearIcon(isFocused());
        }

        @Override
        public void afterTextChanged(Editable s) {}
    });

    // 监听焦点变化
    setOnFocusChangeListener((v, hasFocus) -> {
        updateClearIcon(hasFocus);
    });
}

private void updateClearIcon(boolean hasFocus) {
    boolean shouldShow = hasFocus && !TextUtils.isEmpty(getText());
    Drawable currentRight = getCompoundDrawables()[2];
    if (shouldShow && currentRight != clearDrawable) {
        setCompoundDrawables(getCompoundDrawables()[0], getCompoundDrawables()[1], clearDrawable, getCompoundDrawables()[3]);
    } else if (!shouldShow && currentRight != null) {
        setCompoundDrawables(getCompoundDrawables()[0], getCompoundDrawables()[1], null, getCompoundDrawables()[3]);
    }
}

这个方案把两种状态变化的逻辑统一到一个方法里，确保只有当真正需要变更图标时才执行修改，既解决了无限触发问题，也让代码更简洁。

内容的提问来源于stack exchange，提问作者Justin