关于改变一个控件里的Drawable属性的时候其他控件也一起变化的问题

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android中从同一个资源文件中加载出来的drawable会共享状态，如果你加载出来多个drawable，当改变了其中一个的状态时，其他drawable的状态也会相应改变。

举个栗子哈哈

<Button
      android:id="@+id/button1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_marginTop="100dp"
      android:background="@color/colorPrimary"
      android:onClick="button1"
      android:text="button1" />

  <Button
      android:id="@+id/button2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_marginTop="200dp"
      android:background="@color/colorPrimary"
      android:onClick="button2"
      android:text="button2" />

@Override
protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main2);
   findViewById(R.id.button1).getBackground().setAlpha(0);
}

/**
   * Make this drawable mutable. This operation cannot be reversed. A mutable
   * drawable is guaranteed to not share its state with any other drawable.
   * This is especially useful when you need to modify properties of drawables
   * loaded from resources. By default, all drawables instances loaded from
   * the same resource share a common state; if you modify the state of one
   * instance, all the other instances will receive the same modification.
   *
   * Calling this method on a mutable Drawable will have no effect.
   *

如果把这个drawable变为mutate drawable后，这个drawable就不会与其他drawable共享状态。

@Override
protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main2);
   findViewById(R.id.button1).mutate().getBackground().setAlpha(0);
}

这样设置就没问题了，当然也可以一开始就不要将它们的背景资源文件设成同一个,也可以解决