Question

我有一个带有自定义状态的ImageView子类。实例化窗口小部件时，不会调用onCreateDrawableState，并且图像图形不会出现在我的布局中。即使我调用了refreshDrawableState（），它也不起作用。我单步执行后者并且View代码期望m_background已经设置（在我的情况下它仍然是null）。

我错过了什么会导致m_background有一个初始值？

values / attrs.xml

<resources>
  <declare-styleable 
    name="toggle_states">

    <attr name="state_left" format="boolean"/>
    <attr name="state_right" format="boolean"/>
  </declare-styleable>
</resources>

可绘/ selector_toggle.xml

<selector 
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:myapp="http://schemas.android.com/apk/res/com.example.test" >

   <item 
     myapp:state_left="true"
     android:drawable="@drawable/toggle_left" />

   <item 
     myapp:state_right="true"
     android:drawable="@drawable/toggle_right" />
 </selector>

Toggle.java

public class Toggle extends ImageView 
{
  private static final int[] STATE_LEFT = {R.attr.state_left};
  private static final int[] STATE_RIGHT= {R.attr.state_right};

  public enum State {LEFT, RIGHT};
  private State state = State.LEFT;

  public Toggle (Context context, AttributeSet attrs) 
  {
    super(context, attrs);
  }

  @Override
  public int[] onCreateDrawableState (int extraSpace) 
  {
    final int[] drawableState = super.onCreateDrawableState (extraSpace + 1);
    if (state == State.LEFT)
      mergeDrawableStates (drawableState, STATE_LEFT);
    else
      mergeDrawableStates (drawableState, STATE_RIGHT);
    return drawableState;
  }
}

some_layout.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:myapp="http://schemas.android.com/apk/res/com.example.test"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:orientation="vertical"
  >

  ...

  <com.example.test.Toggle
    android:id="@+id/toggle"
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    myapp:state_left="true"
  />

  ...

</LinearLayout>

Answer 1

你在com.example.test.Toggle

中错过了android:background="@drawable/selector_toggle.xml"

<com.example.test.Toggle
        android:id="@+id/toggle"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:background="@drawable/selector_toggle.xml"
        myapp:state_left="true"
      />

使用自定义状态，从不调用onCreateDrawableState

1 个答案: