ImageSpan 不适用于 Android 5

Question

I have this function that works fine on Android 4.4.1, but breaks on 5.0+.

  public static SpannableStringBuilder prependImage(Drawable drawable, String text) {
    SpannableStringBuilder builder = new SpannableStringBuilder("  " + text);
    builder.setSpan(new ImageSpan(drawable), 0, 1, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
    return builder;
  }

And I use it like this:

class MyButton extends Button {

    // ... snip ...

    setText(
        prependImage(
            getDrawable(imageResource, color),                     
            getContext().getString(stringResource)),
        BufferType.SPANNABLE);

Here is the getDrawable() method referenced above:

 private Drawable getDrawable(int resource, int color) {
    final Resources resources = getContext().getResources();
    Drawable drawable = resources.getDrawable(resource);
    if (drawable != null) {
      drawable.setColorFilter(color, PorterDuff.Mode.SRC_IN);
      drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
    }
    return drawable;
  }

When I debug, everything seems to succeed, but no image is drawn. Any ideas what I might be doing wrong?

Answer 1

By default, in Material buttons are styled to show text in all-caps. However, there is a bug in the AllCapsTransformationMethod used for capitalization that causes it to discard Spannable data.

You can override the default button styling and disable all-caps by specifying android:textAllCaps="false" on your Button.

<Button
    ...
    android:textAllCaps="false" />

have a look here

Answer 2

Your code related to working with Spannables is ok. You can check it by setting text for TextView.

The problem is in material design of button on Android 5.0.

<style name="Widget.Material.Button">
    <item name="background">@drawable/btn_default_material</item>
    <item name="textAppearance">?attr/textAppearanceButton</item>
    <item name="minHeight">48dip</item>
    <item name="minWidth">88dip</item>
    <item name="stateListAnimator">@anim/button_state_list_anim_material</item>
    <item name="focusable">true</item>
    <item name="clickable">true</item>
    <item name="gravity">center_vertical|center_horizontal</item>
</style>

There are two solution.

The first one is just use TextView as your button and setText with image to it.

For another (and may be more correct) you need to extend button style ( Widget.Material.Button ) in next way:

<style name="BtnStyle" parent="android:Widget.Material.Button">
    <item name="android:textAppearance">@null</item>
</style>

Then in your layout:

<Button
    android:id="@+id/test2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Test"
    style="@style/BtnStyle"/>

After you'll do it you should see the images in the button.

Don't forget for Android version that is lower than 5.0 you should create BtnStyle too, but in other resource directory (res/values-v14/style.xml).

Answer 3

Maybe you need to check the content of that Drawable object, you use the getDrawable() to get the Drawable object, but the API definition seems not match your calling parameters.

For Android 5.0+

Drawable getDrawable(int id) This method was deprecated in API level 22. Use getDrawable(int, Theme) instead.

Drawable getDrawable(int id, Resources.Theme theme) Return a drawable object associated with a particular resource ID and styled for the specified theme.

The second parameter looks like to be a Theme, not a color. right ?

Answer 4

try this

 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
      getResources().getDrawable(R.drawable.your_drawable, getTheme());
            } else {
                getResources().
                        getDrawable(R.drawable.your_drawable);
            }

Answer 5

需要注意的一件事，可绘制矢量不起作用，您必须有一个可绘制的 png 或 jpeg 或传递给 ImageSpan 位图