TextView setCompoundDrawables时不生效

项目中遇到TextView setCompoundDrawables时不生效的情况。

不生效原因涉及到setCompoundDrawables的具体实现。

setCompoundDrawables源码如下：

/**
     * Sets the Drawables (if any) to appear to the left of, above, to the
     * right of, and below the text. Use {@code null} if you do not want a
     * Drawable there. The Drawables must already have had
     * {@link Drawable#setBounds} called.
     * <p>
     * Calling this method will overwrite any Drawables previously set using
     * {@link #setCompoundDrawablesRelative} or related methods.
     *
     * @attr ref android.R.styleable#TextView_drawableLeft
     * @attr ref android.R.styleable#TextView_drawableTop
     * @attr ref android.R.styleable#TextView_drawableRight
     * @attr ref android.R.styleable#TextView_drawableBottom
     */
    public void setCompoundDrawables(@Nullable Drawable left, @Nullable Drawable top,
            @Nullable Drawable right, @Nullable Drawable bottom) {

注释中强调：

The Drawables must already have had
* {@link Drawable#setBounds} called.

所以setBounds(left, top, right, bottom)之后在设置setCompoundDrawables就可以显示出来了。