如何使用AlertDialog进行活动？

Question

public void Home (View view){
    AlertDialog.Builder dialog = new AlertDialog.Builder(this);
    dialog.setTitle("Back");
    dialog.setIcon(R.drawable.logo);
    dialog.setCancelable(true);
    dialog.setMessage("Do you want to go back?");
    dialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            Intent intent = new Intent(this, MainActivity.class);
            startActivity(intent);
        }

    });

    dialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

    dialog.show();
}

Now I stay at pageOne.java when I click button "Home". I want to go back to MainActivity.java but I get an error.

Answer 1

Your usage of this is a problem:

new Intent(this, MainActivity.class);

In that scope, it thinks this is referring to the anonymous inner class DialogInterface.OnClickListener . So instead, you should use a reference to your outer class instance like HomeActivity.this (or whatever your activity is called).

new Intent(HomeActivity.this, MainActivity.class);

Answer 2

"this" you used in ClickListener refer to the Click Event Listener.

But need to add is YourActivity.this, and if it is a fragment call getActivity() instead of "this".

I hope it will be OK for you.

  public void Home (View view){
        AlertDialog.Builder dialog = new AlertDialog.Builder(this);
        dialog.setTitle("Back");
        dialog.setIcon(R.drawable.logo);
        dialog.setCancelable(true);
        dialog.setMessage("Do you want to go back?");
        dialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Intent intent = new Intent(pageOne.this, MainActivity.class);
                startActivity(intent);
            }

        });

        dialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });

        dialog.show();
    }

Answer 3

您可以尝试Intent intent = new Intent(pageOne.this, MainActivity.class);

Answer 4

Use getApplicationContext or Activity.this. It is good to use this method.

 Intent in=new Intent(PageOne.this,MainActivity. this);
 startActivity(in);