java - 尝试在触摸时更改图像资源，然后在发布时更改回来

Question

当用户触摸 ImageView 时，我正在更改可绘制资源，当他们释放时，它会恢复为默认值。我在网上复制了一些代码，应该可以工作，但不能。我在收到的错误中发表了评论

final ImageView green = (ImageView) findViewById(R.id.Green);
green.setOnTouchListener(new OnTouchListener() { //cannot resolve symbol setOnTouch...
                          //^^Invalid method declaration return type required
    @Override
    public boolean onTouch(View view, MotionEvent event) { //cannot resolve symbol view/event
        switch (event.getAction()) { //cannot resolve symbol event
            case MotionEvent.ACTION_DOWN: { //constant expression required
                green.setImageResource(R.drawable.green_square);
                break;
            }
            case MotionEvent.ACTION_UP: { //constant expression required
                green.setImageResource(R.drawable.blank_square);
                break;
            }
        }
        return false; // cannot return a value of type void
    }
});

Answer 1

将选择器定义为:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true" android:drawable="@drawable/green_square"/>
    <item android:state_pressed="false" android:drawable="@drawable/blank_square"/>
</selector>

并在布局 xml 中，将 src 设置为上面的选择器。