Question

我在一个叫做“ViewBreakout”的类中设置了一个警告对话框，我按钮设置正常，它创建了按钮但是当我尝试添加一个意图时，我收到一条错误消息 “构造函数Intent（new DialogInterface.OnClickListener（）{}，Class）未定义” 。它提供的解决方案是删除匹配intent（）; ???

的参数

    AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(getContext());
    dialogBuilder.setTitle("UNLUCKY :(");
    dialogBuilder.setMessage("You lost all your lives");
    dialogBuilder.setPositiveButton("try again", new DialogInterface.OnClickListener() {

        @Override
        public void onClick(DialogInterface dialog, int which) {
            // TODO Auto-generated method stub

            Intent i = new Intent (this, main.class);//get error here
            startActivity(i);
        }
    });
    AlertDialog alertDialog = dialogBuilder.create();
    alertDialog.show();

以下是包含该类的代码，当另一个类的全局变量等于0时，设置alertDialog。我真的被卡住了，很快就会出现一个uni项目。

这是我班上的代码。我想我会告诉全班同学，看看是否有遗失的东西

    /**
    * Displays a graphical view of the game of breakout
    */


    class ViewBreakout extends View implements OnTouchListener, Observer
    {
    // private static final long serialVersionUID = 1L;
    private ControllerBreakout breakoutController;
    private GameObject       ball;
    private GameObject[]     bricks;
    private GameObject       bat;
    private int              score;
    private long             frames = 0;
    private Paint            paint  = new Paint();
    private boolean isBall = true;



    public ViewBreakout(Context context)
    {
    super(context);
    Debug.trace("View Breakout");
    setFocusable(true);
    setFocusableInTouchMode(true);      //

    this.setOnTouchListener(this);      // Take touch actions

    paint.setColor(Color.BLACK);    // Paint colour
    paint.setAntiAlias(true);       // Better quality
    if ( W < 600)
     paint.setTextSize(30);        // Text size
    else
    paint.setTextSize(40);


    }

    /**
    * Code called to draw the current state of the game Uses 
    *    paint.setColor -- set paint colour
    *     drawRect:      -- Draw rectangle 
    *    setPaint:      -- Colour used 
    *    drawText:      -- Write string on display
    */
    @Override
    public void onDraw(Canvas canvas)
    {
    frames++;


     paint.setColor(Color.DKGRAY);    // Paint colour
     canvas.drawRect(0, 0, W, H, paint);

     //if lives is 0 then display message
     if(LIVES <= 0){
    AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(getContext());
    dialogBuilder.setTitle("UNLUCKY :(");
    dialogBuilder.setMessage("You lost all your lives");
    dialogBuilder.setPositiveButton("try again", new DialogInterface.OnClickListener() {

        @Override
        public void onClick(DialogInterface dialog, int which) {
            // TODO Auto-generated method stub

            Intent i = new Intent (this, main.class);
            startActivity(i);
        }
    });
    AlertDialog alertDialog = dialogBuilder.create();
    alertDialog.show();

}

Answer 1

您的意图是在另一个类内部类OnClickListener内创建的。因此“this”指的是您的匿名内部类OnClickListener的实例。

通过以下方式更改：

Intent i = new Intent (MyActivity.this, main.class);

编辑：

//添加上下文变量

private Context myContext;

public ViewBreakout(Context context){ 
       //your stuff
       this.myContext = context;
}

Intent i = new Intent (myContext, main.class);

Answer 2

使用活动上下文代替此

      Intent i = new Intent (ActivityName.this, main.class);

其中ActivityName是活动类的名称，例如MainActivity

如果在非活动上下文中使用intent，则将上下文传递给该类的构造函数并使用上下文。开始活动也是如此。使用上下文在非活动类context.startActivity（i）;

中启动活动

   Context mContext;  
   public ViewBreakout(Context context)
   {
   super(context);
   mContext= context; 
   ....   
   }
   .....
       @Override
    public void onClick(DialogInterface dialog, int which) {
       Intent i = new Intent (mContext, main.class);
       mContext.startActivity(i); 
    }
});

如何在alertDialog中单击按钮启动活动

2 个答案: