来自活动的Android片段文本视图setText

我有一个问题：我有两个标签的TabLayout。一个选项卡包含文本视图。 我想稍后从MainActivity中的线程更改MainActivity中TextView的文本。但它抛出了一个NPE，我不知道如何解决它

以下是我的MainActivity.java-code：

public class MainActivity extends AppCompatActivity {

private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;

public static ThreadConnected myThreadConnected;
TabTerminal tabT;

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

    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(mViewPager);

    tabT = new TabTerminal();
    tabT.setText("324");
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        //Returning the current tabs
        switch (position) {
            case 0:
                TabControl tab1 = new TabControl();
                return tab1;
            case 1:
                TabTerminal tab2 = new TabTerminal();
                return tab2;
            default:
                return null;
        }
    }

    @Override
    public int getCount() {
        return 2;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        // ...
    }
}

}

下面是带有TextView的片段：

public class TabTerminal extends Fragment {

static TextView txtterminalout;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.tab_terminal, container, false);
    TextView txtterminalout = (TextView) rootView.findViewById(R.id.terminalout);

    return rootView;
}

public void setText(String text) {
    TextView t = (TextView) getView().findViewById(R.id.terminalout);
    t.setText(text);
}

}

您可以在main活动的片段中调用setText方法，如下所示：

FragmentManager fm = getSupportFragmentManager();

//if you added fragment via layout xml
YourFragmentClass fragment =  (YourFragmentClass)fm.findFragmentById(R.id.your_fragment_id);
fragment.setText();

YourFragmentClass fragment = (YourFragmentClass)fm.findFragmentByTag("yourTag");

如果您通过代码添加了片段，并且在添加片段时使用了标记字符串，请改用findFragmentByTag，如下所示：

FragmentManager fm = getSupportFragmentManager();

//if you added fragment via layout xml
YourFragmentClass fragment =  (YourFragmentClass)fm.findFragmentById(R.id.your_fragment_id);
fragment.setText();

YourFragmentClass fragment = (YourFragmentClass)fm.findFragmentByTag("yourTag");

希望有帮助。

在onCreate的末尾，您正在创建新的片段并尝试将其设置为text。因为它没有膨胀，所以你得到NPO

你们想要的是抓住已经膨胀的碎片并在上面设置文本。

---

请尝试getSupportFragmentManager.findFragmentByIdR.id.your_fragment.setText

是否可以添加异常详细信息？getView似乎返回null。在MainActivity的onResume中调用此方法，在案例1中：return选项卡；而不是创建新的TabTerminal