Android自定义Toast，多次弹出时取消上次弹出，最后一次弹出为准

 
public abstract class Toast {
    public static final int LENGTH_SHORT = android.widget.Toast.LENGTH_SHORT;
    public static final int LENGTH_LONG = android.widget.Toast.LENGTH_LONG;
  
    private static android.widget.Toast toast;
    private static Handler handler = new Handler();
  
    private static Runnable run = new Runnable() {
        public void run() {
            toast.cancel();
        }
    };
  
    private static void toast(Context ctx,CharSequence msg,int duration) {
        handler.removeCallbacks(run);
        // handler的duration不能直接对应Toast的常量时长，在此针对Toast的常量相应定义时长
        switch (duration) {
        case LENGTH_SHORT:// Toast.LENGTH_SHORT值为0，对应的持续时间大概为1s
            duration = 1000;
            break;
        case LENGTH_LONG:// Toast.LENGTH_LONG值为1，对应的持续时间大概为3s
            duration = 3000;
            break;
        default:
            break;
        }
        if (null != toast) {
            toast.setText(msg);
        } else {
            toast = android.widget.Toast.makeText(ctx,msg,duration);
        }
        handler.postDelayed(run,duration);
        toast.show();
    }
  
    /**
     * 弹出Toast
     * 
     * @param ctx
     *            弹出Toast的上下文
     * @param msg
     *            弹出Toast的内容
     * @param duration
     *            弹出Toast的持续时间
     */
    public static void show(Context ctx,int duration)
            throws NullPointerException {
        if (null == ctx) {
            throw new NullPointerException("The ctx is null!");
        }
        if (0 > duration) {
            duration = LENGTH_SHORT;
        }
        toast(ctx,duration);
    }
  
    /**
     * 弹出Toast
     * 
     * @param ctx
     *            弹出Toast的上下文
     * @param msg
     *            弹出Toast的内容的资源ID
     * @param duration
     *            弹出Toast的持续时间
     */
    public static void show(Context ctx,int resId,ctx.getResources().getString(resId),duration);
    }
  
}