Android dialog提示框 android警告框

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                builder.setTitle("提示");
                builder.setIcon(R.drawable.a1);
                builder.setMessage("确定要删除吗？");

                builder.setPositiveButton("确定", new OnClickListener() {

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

                    }
                });

                builder.setNegativeButton("取消", new OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub
                        dialog.dismiss(); // 取消对话框
                    }
                });

                AlertDialog dialog = builder.create();
                dialog.show(); // 显示对话框
            }
        });
    }