BackStack无法正常工作

Question

这是我的MainActivity.java类，我想使用backstack在我的片段和活动之间导航。我使用了addToBackStack（null）和popbackStack0，仍然无法正常工作。

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener, OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        //ImageView imageView=(ImageView) findViewById(R.id.mainpage);
        //imageView.setImageResource(R.drawable.banner);

       Button button1 = (Button) findViewById(R.id.cropbutton);
        button1.setOnClickListener(this);
        Button button2 = (Button) findViewById(R.id.diseasebutton);
        button2.setOnClickListener(this);
        Button button3 = (Button) findViewById(R.id.pestbutton);
        button3.setOnClickListener(this);
        Button button5 = (Button) findViewById(R.id.expertbutton);
        button5.setOnClickListener(this);



        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }
    //boolean doubleBackToExitPressedOnce = false;

    @Override
    public void onBackPressed()
    {


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();
        Button button1 = (Button) findViewById(R.id.cropbutton);
        Button button2 = (Button) findViewById(R.id.diseasebutton);
        Button button3=(Button) findViewById(R.id.pestbutton);
        Button button5 = (Button) findViewById(R.id.expertbutton);
        if (id == R.id.nav_camera) {
            Cropfragment cropfragment=new Cropfragment();
            FragmentManager manager=getSupportFragmentManager();
            manager.beginTransaction().replace(R.id.relative1,cropfragment,cropfragment.getTag()).addToBackStack(null).commit();
            manager.popBackStack("relative1",0);

        } else if (id == R.id.nav_gallery) {
            BlankFragment blankFragment=new BlankFragment();
            FragmentManager manager=getSupportFragmentManager();
            manager.beginTransaction().replace(R.id.relative1,blankFragment,blankFragment.getTag()).addToBackStack(null).commit();
            manager.popBackStack("relative1",0);

        }  else if (id == R.id.nav_home) {
            Intent appInfo = new Intent(MainActivity.this, MainActivity.class);
            startActivity(appInfo);

        } else if (id == R.id.nav_pesti) {
            pest blankFragment=new pest();
            FragmentManager manager=getSupportFragmentManager();
            manager.beginTransaction().replace(R.id.relative1,blankFragment,blankFragment.getTag()).addToBackStack(null).commit();
            manager.popBackStack("relative1",0);

        }
        else if (id == R.id.nav_expert) {

            Intent appInfo = new Intent(MainActivity.this, detail_expert.class);

            startActivity(appInfo);
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }


    @Override
    public void onClick(View v) {
        Button button1 = (Button) findViewById(R.id.cropbutton);
        Button button2 = (Button) findViewById(R.id.diseasebutton);
        Button button3=(Button) findViewById(R.id.pestbutton);
        Button button5 = (Button) findViewById(R.id.expertbutton);
        switch (v.getId()) {

            case R.id.cropbutton:
                Cropfragment cropfragment = new Cropfragment();
            FragmentManager manager = getSupportFragmentManager();
            manager.beginTransaction().replace(R.id.relative1, cropfragment, cropfragment.getTag()).addToBackStack(null).commit();
                manager.popBackStack("relative1", 0);
                break;

            case R.id.diseasebutton:
                BlankFragment blankFragment= new BlankFragment();
                FragmentManager manager1 = getSupportFragmentManager();
                manager1.beginTransaction().replace(R.id.relative1,blankFragment,blankFragment.getTag()).addToBackStack(null).commit();
                manager1.popBackStack("relative1",0);
                break;

            case R.id.pestbutton:
                pest pestFragment= new pest();
                FragmentManager manager2 = getSupportFragmentManager();
                manager2.beginTransaction().replace(R.id.relative1,pestFragment,pestFragment.getTag()).addToBackStack(null).commit();
                manager2.popBackStack("relative1",0);
                break;

            case R.id.expertbutton:
                Intent appInfo1 = new Intent(MainActivity.this, detail_expert.class);
                startActivity(appInfo1);
                break;

            default:
                break;
        }

    }

}

Answer 1

查看代码我不确定你想要如何导航，但是通过代码，我相信你正在添加带有null的addbackstack并使用标记删除，所以添加标记而不是null然后使用标记{{1或者，只需要执行popbackstack（）或者如果你想对manager.popBackStack("relative1",0);做同样的事情，那么你需要覆盖`onBackPress（），获取片段的大小并在此活动中逐个弹出。