在活动中使用 OnBackPressed 方法的一个片段到另一个片段答案

【问题标题】：One fragment To Another fragment using OnBackPressed method in activity在活动中使用 OnBackPressed 方法的一个片段到另一个片段
【发布时间】：2021-11-23 01:52:10
【问题描述】：

我的问题很简单，当我按下返回按钮时，它将转到上一个片段，我该怎么做？当我在对话中单击“是”按钮时，如果我单击没有进入前一个片段的按钮，它将完成显示..

@Override
    public void onBackPressed() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(false);
        builder.setMessage("Do you want to Exit?");
        builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                //if user pressed "yes", then he is allowed to exit from application
                finish();
            }
        });
        builder.setNegativeButton("No",new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                //if user select "No", just cancel this dialog and continue with app
                dialog.cancel();
            }
        });
        AlertDialog alert=builder.create();
        alert.show();

    }

【问题讨论】：

标签： android android-fragments modal-dialog android-alertdialog android-fragmentactivity

【解决方案1】：

首先如果你提交任何片段添加 addToBackStack()

getSupportFragmentManager().beginTransaction().addToBackStack(null).replace(R.id.nav_host_fragment,new NewFragment()).commit();

然后

        @Override
        public void onBackPressed() {
          if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
              getSupportFragmentManager().popBackStack();
          } else {
              AlertDialog.Builder builder = new AlertDialog.Builder(this);
              builder.setCancelable(false);
              builder.setMessage("Do you want to Exit?");
              builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                  
                  @Override
                  public void onClick(DialogInterface dialog, int which) {
                      //if user pressed "yes", then he is allowed to exit from application
                      finish();
                  }
              });
              builder.setNegativeButton("No",new DialogInterface.OnClickListener() {
                  
                  @Override
                  public void onClick(DialogInterface dialog, int which) {
                      //if user select "No", just cancel this dialog and continue with app
                      dialog.cancel();
                  }
              });

              AlertDialog alert=builder.create();
              alert.show();
          }
        }

【讨论】：