Question

我有一个非常简单的＆＃39; CustomButton＆＃39;扩展默认＆＃39;按钮＆＃39;类。我的CustomButton使用onTouchEvent，我想将一个函数从我的Activity传递给CustomButton并在触摸时执行它。

CustomButton类工作正常，但我似乎无法弄清楚如何将函数传递给它。

的活动：

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＆＃39;数据类型＆＃39;例如＆＃39;功能＆＃39;我可以用于此目的还是有不同的方法如何实现这一目标？谢谢！

Answer 1

当您想在Java中执行操作时，通常需要一个对象和一个函数。这就是Interfaces的用途。您声明一个具有函数名称的接口。您的Activity实现了此接口和函数，然后您将活动实例传递给按钮。在您的情况下，您可能正在寻找OnTouchListener或OnClickListener？如果你想拥有一个特殊的界面，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!" );
    }
}

修改

要保持按钮内的逻辑，你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 }

在可扩展按钮类中实现回调

1 个答案: