简单地在onKeyUp()中做:

@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {

    if (keyCode == KeyEvent.KEYCODE_BACK) {
        // do something
        return true;  // return true if back handled, false otherwise
    }

    return super.onKeyUp(keyCode, event);
}

   @Override
   public boolean onKeyDown(int keyCode, KeyEvent event)
    {
       if ((keyCode == KeyEvent.KEYCODE_BACK))
  {
           finish();
    }
       return super.onKeyDown(keyCode, event);
    }

注释任何下键相关的方法现在addToBackStack将工作。 谢谢

if片段和使用NavController简单调用

findNavController().popBackStack()

最好的解决方案,

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;

public class BaseActivity extends AppCompatActivity {
    @Override
    public void onBackPressed() {

        FragmentManager fm = getSupportFragmentManager();
        for (Fragment frag : fm.getFragments()) {
            if (frag == null) {
                super.onBackPressed();
                finish();
                return;
            }
            if (frag.isVisible()) {
                FragmentManager childFm = frag.getChildFragmentManager();
                if (childFm.getFragments() == null) {
                    super.onBackPressed();
                    finish();
                    return;
                }
                if (childFm.getBackStackEntryCount() > 0) {
                    childFm.popBackStack();
                    return;
                }
                else {

                    fm.popBackStack();
                    if (fm.getFragments().size() <= 1) {
                        finish();
                    }
                    return;
                }

            }
        }
    }
}

private boolean isMainFragment = true;

@Override
public void onBackPressed() {

    if (isMainFragment){
        finish();
    }else {
        getSupportFragmentManager().popBackStack();
        isMainFragment = true;
    }
}

当打开花药片段时，只需添加

isMainFragment = false;

这是我的工作

在片段的onCreate方法中添加以下内容:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    OnBackPressedCallback callback = new OnBackPressedCallback(true) {
        @Override
        public void handleOnBackPressed() {
            //Handle the back pressed
        }
    };
    requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
}