一个“Toast”引发的bug

//就是定义一个全局的成员变量Toast, 这个Toast不为null的时候才去make,否则直接setText.
//为了按返回键后立即使Toast不再显示，重写父类Activity的onBackPressed()方法里面去cancel你的Toast即可
private Toast mToast;
    public void showToast(String text) {  
        if(mToast == null) {  
            mToast = Toast.makeText(MobileSendTopicActivity.this, text, Toast.LENGTH_SHORT);  
        } else {  
            mToast.setText(text);    
            mToast.setDuration(Toast.LENGTH_SHORT);  
        }  
        mToast.show();  
    }  
      
    public void cancelToast() {  
            if (mToast != null) {  
                mToast.cancel();  
            }  
    }  
      
    public void onBackPressed() {  
            cancelToast();  
            super.onBackPressed();
    }  

按照他的思路，我就在自己的项目里去实现，但是由于我的项目里有自定义的Toast（通过new Toast（context）的方法实现）和Toast.makeText(context,message, duration).show();不同，两种混合使用，就会在程序中报类似以下错误：

为了避免这种错误，要么不用自定义的Toast（不可能），要么全部用自定义的（工作量有点大，不想改），所以我就在类中定义了两个全局成员变量

private static Toast mToast;
private static Toast mCustomToast;

下面贴上我的Tst.java代码：

public class Tst {
    private Tst() {
        /* cannot be instantiated */
        throw new UnsupportedOperationException("cannot be instantiated");
    }
    private static Toast mToast;
    private static Toast mCustomToast;
    private static Toast initToast(Context context,CharSequence message, int duration) {
        if (mToast == null) {
            mToast = Toast.makeText(context, message,duration);
        }
        mToast.setText(message);
        mToast.setDuration(duration);
     return mToast;
    }
    private static Toast initToast(Context context,int message, int duration) {
        if (mToast == null) {
            mToast = Toast.makeText(context, message,duration);
        }
        mToast.setText(message);
        mToast.setDuration(duration);
        return mToast;
    }
    private static Toast initCustomToast(Context context, CharSequence message, ToastType toastType, int duration) {
        LinearLayout toastView = initToastView(context, message, toastType);
        if (mCustomToast == null) {
            mCustomToast = new Toast(context);
        }
        mCustomToast.setGravity(Gravity.CENTER, 0, 0);
        mCustomToast.setDuration(duration);
        mCustomToast.setView(toastView);
        return mCustomToast;
    }
    /**
     * 短时间显示Toast
     * @param context
     * @param message
     */
    public static void showShort(Context context, CharSequence message) {
        initToast(context,message,Toast.LENGTH_SHORT).show();
    }
    /**
     * 短时间显示Toast
     * @param context
     * @param message
     */
    public static void showShort(Context context, int message) {
        initToast(context,message,Toast.LENGTH_SHORT).show();
    }
    /**
     * 自定义view Toast
     */
    public static void showShort(Context context, CharSequence message, ToastType toastType) {
        initCustomToast(context, message, toastType, Toast.LENGTH_SHORT).show();
    }
    /**
     * 长时间显示Toast
     * @param context
     * @param message
     */
    public static void showLong(Context context, CharSequence message) {
        initToast(context,message,Toast.LENGTH_LONG).show();
    }
    /**
     * 长时间显示Toast
     * @param context
     * @param message
     */
    public static void showLong(Context context, int message) {
        initToast(context,message,Toast.LENGTH_LONG).show();
    }
    public static void showLong(Context context, CharSequence message, ToastType toastType) {
        initCustomToast(context, message, toastType, Toast.LENGTH_LONG).show();
    }
    /**
     * 自定义显示Toast时间
     * @param context
     * @param message
     * @param duration
     */
    public static void show(Context context, CharSequence message, int duration) {
        initToast(context,message,duration).show();
    }
    /**
     * 自定义显示Toast时间
     * @param context
     * @param message
     * @param duration
     */
    public static void show(Context context, int message, int duration) {
        initToast(context,message,duration).show();
    }
    public static void show(Context context, int msgId, int duration, ToastType toastType) {
        CharSequence message = context.getResources().getText(msgId);
        initCustomToast(context,message,toastType ,duration).show();
    }
    private static LinearLayout initToastView(Context context, CharSequence message, ToastType toastType) {
        int resId;
        int dp2px10 = DensityUtils.dp2px(context, 10);
        LinearLayout layout = new LinearLayout(context);
        layout.setBackgroundResource(R.drawable.bg_toast);
        layout.setOrientation(LinearLayout.VERTICAL);
        layout.setMinimumWidth(DensityUtils.dp2px(context, 122));
        ImageView imageCodeProject = new ImageView(context);
        switch (toastType) {
            default:
            case DONE:
                resId = R.drawable.icon_toast_done;
                break;
            case WARNING:
                resId = R.drawable.icon_toast_warning;
                break;
        }
        imageCodeProject.setImageResource(resId);
        LinearLayout.LayoutParams layoutParams1 = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT);
        layoutParams1.setMargins(0, dp2px10 * 2, 0, 0);
        layout.addView(imageCodeProject, layoutParams1);
        LinearLayout.LayoutParams layoutParams2 = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT);
        layoutParams2.setMargins(dp2px10, DensityUtils.dp2px(context, 14) , dp2px10, DensityUtils.dp2px(context, 22));
        TextView textView = new TextView(context);
        textView.setText(message);
        textView.setTextColor(Color.WHITE);
        textView.setGravity(Gravity.CENTER_HORIZONTAL);
        layout.addView(textView, layoutParams2);
        return layout;
    }
}