在Activity的Fragment中设置EditText的文本

Question

如何从 Activity 中设置 Fragment 的 EditText 的文本？

这里是活动代码：

public class MainActivity extends AppCompatActivity 
{
    FrameLayout simpleFrameLayout;
    TabLayout tabLayout;
    EditText editText;
    
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        simpleFrameLayout = (FrameLayout) findViewById(R.id.simpleFrameLayout);
        tabLayout = (TabLayout) findViewById(R.id.simpleTabLayout);
// Create a new Tab named "First"
        TabLayout.Tab firstTab = tabLayout.newTab();
        firstTab.setText("Personal"); // set the Text for the first Tab
        tabLayout.addTab(firstTab); // add  the tab at in the TabLayout
// Create a new Tab named "Second"
        TabLayout.Tab secondTab = tabLayout.newTab();
        secondTab.setText("Chat"); // set the Text for the second Tab
        tabLayout.addTab(secondTab); // add  the tab  in the TabLayout
        
        
        
        try {
            Fragment fragment = null;
            fragment = new FirstFragment();
            FragmentManager fm = getSupportFragmentManager();
            FragmentTransaction ft = fm.beginTransaction();
            ft.replace(R.id.simpleFrameLayout, fragment);
            ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
            ft.commit();
        }
        catch (Exception e) {

        }
        
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
                @Override
                public void onTabSelected(TabLayout.Tab tab) {
// get the current selected tab's position and replace the fragment accordingly
                    try {
                        Fragment fragment = null;
                    switch (tab.getPosition()) {
                        case 0:
                            fragment = new FirstFragment();
                            break;
                        case 1:
                            fragment = new SecondFragment();
                            break;
                    }
                        FragmentManager fm = getSupportFragmentManager();
                        FragmentTransaction ft = fm.beginTransaction();
                    ft.replace(R.id.simpleFrameLayout, fragment);
                    ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
                        ft.commit();
                    }
                    catch (Exception e) {
                        
                    }
                }

                @Override
                public void onTabUnselected(TabLayout.Tab tab) {

                }

                @Override
                public void onTabReselected(TabLayout.Tab tab) {

                }
            });
        
    }
    
    public void connect(){
        //set text of EditText of SecondFragment
    }
}

我正在寻找解决此问题的方法： 我想创建一个聊天客户端，为此我需要不时更新选项卡的 EditText 而无需切换到该选项卡。我还需要在切换标签时不丢失该 EditText 的内容。

Answer 1

只需在主要活动中创建一个变量，您就可以从片段中更新它。由于活动的生命周期不会从一个片段更改为另一个片段，因此您可以从第二个片段中获取相同的值。

我希望这会有所帮助。

Answer 2

假设您不想使用 ViewPager 和 PagerAdapter（您不需要在标签之间滑动），它应该是这样的：

public class MainActivity extends AppCompatActivity 
{
    FrameLayout simpleFrameLayout;
    TabLayout tabLayout;
    EditText editText;

    FirstFragment firstFragment;
    SecondFragment secondFragment;

    private int selectedTabIndex = 0;
    
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        simpleFrameLayout = findViewById(R.id.simpleFrameLayout);
        tabLayout = findViewById(R.id.simpleTabLayout);

        TabLayout.Tab firstTab = tabLayout.newTab();
        firstTab.setText("Personal");
        tabLayout.addTab(firstTab);

        TabLayout.Tab secondTab = tabLayout.newTab();
        secondTab.setText("Chat");
        tabLayout.addTab(secondTab);

        FragmentManager fm = getSupportFragmentManager();

        if (savedInstanceState == null) {
            firstFragment = new FirstFragment();
            secondFragment = new SecondFragment();

            fm.beginTransaction()
              .add(R.id.simpleFrameLayout, firstFragment, "firstFragment")
              .add(R.id.simpleFrameLayout, secondFragment, "secondFragment");
              .detach(secondFragment)
              .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
              .commitNow();
        } else {
            firstFragment = (FirstFragment) fm.findFragmentByTag("firstFragment");    
            secondFragment = (SecondFragment) fm.findFragmentByTag("secondFragment");

            this.selectedTabIndex = savedInstanceState.getInt("selectedTabIndex", 0);
            // selectTab(selectedTabIndex); // you don't need this line
        }
        
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
                @Override
                public void onTabSelected(TabLayout.Tab tab) {
                    this.selectedTabIndex = tab.getPosition();
                    selectTab(selectedTabIndex);
                }

                @Override
                public void onTabUnselected(TabLayout.Tab tab) {

                }

                @Override
                public void onTabReselected(TabLayout.Tab tab) {

                }
            });
    }

    private void selectTab(int selectedTabIndex) {
        FragmentManager fm = getSupportFragmentManager();

        if (selectedTabIndex == 0) {
            fm.beginTransaction()
              .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
              .detach(secondFragment)
              .attach(firstFragment)
              .commitAllowingStateLoss();
        } else if(selectedTabIndex == 1) {
            fm.beginTransaction()
              .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
              .detach(firstFragment)
              .attach(secondFragment)
              .commitAllowingStateLoss();
        }
    }
    
    public void connect(){
        secondFragment.updateText("someText"); // this can run when secondFragment has no view!
    }
}

注意：如果您需要使用更多选项卡，那么您可以使用数组，但您仍然需要初始化/重新初始化，如本 sn-p 所示。

Answer 3

基于您的一般问题的一般答案 使您的编辑文本公开静态public static EditText editText; 为它分配一个值，然后像MainActivity.editText.setText(""); 一样从任何其他类调用它 ` 仅在绝对必要时才使用此方法，因为它可能会导致内存泄漏，因为您必须在使用后手动销毁/取消对象