在可扩展按钮类中实现回调

Question

我有一个非常简单的“CustomButton”类，它扩展了默认的“Button”类。我的 CustomButton 使用 onTouchEvent 并且我想将一个函数从我的 Activity 传递给 CustomButton 并让它在触地时执行。

CustomButton 类工作正常，但我似乎不知道如何将函数传递给它。

活动：

public class mainActivity extends Activity
{
    @Override
    public void onCreate( Bundle savedInstanceState )
    {
        super.onCreate( savedInstanceState );

        Context context = getApplicationContext();
        setContentView( R.layout.main );

        LinearLayout root = (LinearLayout) findViewById( R.id.myLayout   );   
        View child1 = getLayoutInflater().inflate( R.layout.child, null );

        // Define the button
        final CustomButtom myCustomButton = (CustomButtom)child1.findViewById( R.id.button_id );   

        myCustomButtom.setCallback( test ); // <-- I want to pass my 'test' function to CustomButton class, 
                                            //     so it can get executed by the onTouchEvent

        root.addView( myCustomButton );

        super.onCreate( savedInstanceState );
    }

    private int test()
    {
        Log.d( "test", "Callback executed!" );
    }
}

这是我的 CustomButton 类：

public class CustomButtom extends Button
{
    private Function callback;

    public CustomButtom(Context context, AttributeSet attrs) {
        super(context, attrs);

        this.setOnTouchListener
        (
            new OnTouchListener() 
            {
                @Override
                public boolean onTouch(View v, MotionEvent event) 
                {
                    if(event.getAction() == MotionEvent.ACTION_DOWN) 
                    {
                        executeCallback(); // <-- My callback would get executed from here
                    } 

                    return true;
                }
            }
        );

    }

    public void setCallback(Function function)
    {
         callbackFunction = function; // Save the callback in a local variable
    }

    private boolean executeCallback()
    {
        return callbackFunction.execute(); // execute the callback
    }
}

是否有我可以用于此目的的“数据类型”，例如“功能”，或者有不同的方法来实现这一点？谢谢！

Answer 1

当你想在 Java 中执行一个动作时，你通常需要一个对象和一个函数。这就是接口的用途。你用你的函数名声明一个接口。你的 Activity 实现了这个接口和函数，然后你将你的 Activity 实例传递给按钮。在您的情况下，您可能正在寻找 OnTouchListener 或 OnClickListener？如果你想有一个特殊的接口，你可以用同样的方式声明它。

public class mainActivity extends Activity implements OnClickListener
{
    @Override
    public void onCreate( Bundle savedInstanceState )
    {
        super.onCreate( savedInstanceState );

        // I do not see any reason to use the Application Context here. Your Activity has the right context for your UI
        // Context context = getApplicationContext();
        setContentView( R.layout.main );

        LinearLayout root = (LinearLayout) findViewById( R.id.myLayout   );   
        View child1 = getLayoutInflater().inflate( R.layout.child, null );

        // Define the button
        final CustomButtom myCustomButton = (CustomButtom)child1.findViewById( R.id.button_id );   

        myCustomButtom.setOnClickListener(this);

        root.addView( myCustomButton );

        // you did this already
        //super.onCreate( savedInstanceState );
    }

    public void onClick(View v)
    {
        Log.d( "test", "Callback executed!" );
    }
}

编辑：

要保留按钮内部的逻辑，您可以创建自己的界面（OnClickListener 是一个界面），如下所示：

public interface OnCustomActionListener {
    // you can remove the button as parameter if you do not care which button the action came from 
    void onCustomAction(CustomButton button);
}

public class CustomButtom extends Button {
    OnCustomActionListener onCustomActionListener;

    public void setOnCustomActionListener(OnCustomActionListener listener) {
        this.onCustomActionListener = listener;
    }

    /* Creator like in your question mentioned */

    private boolean executeCallback() {
        if (this.onCustomActionListener != null) {
            this.onCustomActionListener.onCustomAction(this);
        }
    }
}

在您的活动中：

public class mainActivity extends Activity implements OnCustomActionListener {
...
     myCustomButtom.setOnCustomActionListener(this);
...
public void onCustomAction(CustomButton button) {
     // do something
}