java - Android - 按住按钮时重复功能

Question

在我的 Android 项目中，我试图重复这段代码(我的 MainActivity.class 文件中的一个函数):

public void positionChange(View v)
{
    findViewById(R.id.player1).setX(findViewById(R.id.player1).getX() - 30);
    findViewById(R.id.player2).setX(findViewById(R.id.player2).getX() + 30);

}

按住按钮时。

目前，当使用以下方法按下按钮时，每次点击都会调用此代码:

android:onClick="positionChange"

在我的 activity_main.xml 文件中。由于我是 Android 编程的新手，我不知道该怎么做，而且我发现的现有代码似乎不能正常工作，那么我怎么才能让它工作呢？

谢谢。

Answer 1

首先您必须知道，每次调用 findViewById() 都会浪费您应用程序的大量时间，因此您最好获取一次并多次使用它们。

要在按住按钮时重复此代码，您必须使用以下链接并使用此链接提供的自定义监听器:

Android - Hold Button to Repeat Action

为了方便起见，我复制了代码:

import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;

/**
* A class, that can be used as a TouchListener on any view (e.g. a Button).
* It cyclically runs a clickListener, emulating keyboard-like behaviour. First
* click is fired immediately, next one after the initialInterval, and subsequent
* ones after the normalInterval.
*
* <p>Interval is scheduled after the onClick completes, so it has to run fast.
* If it runs slow, it does not generate skipped onClicks. Can be rewritten to
* achieve this.
*/
public class RepeatListener implements OnTouchListener {

private Handler handler = new Handler();

private int initialInterval;
private final int normalInterval;
private final OnClickListener clickListener;

private Runnable handlerRunnable = new Runnable() {
    @Override
    public void run() {
        handler.postDelayed(this, normalInterval);
        clickListener.onClick(downView);
    }
};

private View downView;

/**
 * @param initialInterval The interval after first click event
 * @param normalInterval The interval after second and subsequent click 
 *       events
 * @param clickListener The OnClickListener, that will be called
 *       periodically
 */
public RepeatListener(int initialInterval, int normalInterval, 
        OnClickListener clickListener) {
    if (clickListener == null)
        throw new IllegalArgumentException("null runnable");
    if (initialInterval < 0 || normalInterval < 0)
        throw new IllegalArgumentException("negative interval");

    this.initialInterval = initialInterval;
    this.normalInterval = normalInterval;
    this.clickListener = clickListener;
}

public boolean onTouch(View view, MotionEvent motionEvent) {
    switch (motionEvent.getAction()) {
    case MotionEvent.ACTION_DOWN:
        handler.removeCallbacks(handlerRunnable);
        handler.postDelayed(handlerRunnable, initialInterval);
        downView = view;
        downView.setPressed(true);
        clickListener.onClick(view);
        return true;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_CANCEL:
        handler.removeCallbacks(handlerRunnable);
        downView.setPressed(false);
        downView = null;
        return true;
    }

    return false;
}

}

然后在您的 onCreate() 中像下面这样使用它:

View player1 =  findViewById(R.id.player1);
View player2 =  findViewById(R.id.player2);
button.setOnTouchListener(new RepeatListener(400, 100, new OnClickListener() {
@Override
public void onClick(View view) {
  // the code to execute repeatedly
  player1.setX(player1.getX() - 30);
  player2.setX(player2.getX() + 30);
}
}));

为了获得更好的代码，您可以将 player1 和 player2 定义为 public(在您的 onCreate 之外)，然后在 onCreate() 中启动它们