Java 安卓碎片——”；“活动已被销毁”；在片段中按文本后

因此，我一直在尝试在我的应用程序中实现一个功能，当我从

searchBoxResultsFragment

中单击一个用户名时，该用户名是显示搜索框用户结果的一个片段，它将转到用户的配置文件

用户的配置文件将被放置在名为

UserFragment

的新片段中。因此，基本上，

searchBoxResultsFragment

将被

UserFragment

替换。因此，我在调用函数中使用了

ft.replace（）

，为

UserFragment

创建了一个新实例，它位于

MainNavigation

活动类的

UserFragment（）

函数中

但是，我运行时遇到一个错误

活动已被破坏

，导致我的应用程序崩溃

我是Android开发新手，正在自学如何开发应用程序

以下是我的代码：

MainNavigation.java

public class MainNavigation extends AppCompatActivity {

    private BottomNavigationView mBottomNav;

    // fix main layout of navigation
    ImageButton uProfileBtn, searchBox;

    GetSearchBoxResults getSearcResults;

    EditText searchBoxText;

    Fragment frag = null;


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

        // hide action bar
        if(this.getSupportActionBar()!=null) {
            this.getSupportActionBar().hide();
        }

        uProfileBtn = (ImageButton) findViewById(R.id.profileBtn);
        searchBox = (ImageButton) findViewById(R.id.searchFriendBtn);

        mBottomNav = (BottomNavigationView) findViewById(R.id.navigation);
        mBottomNav.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                selectFragment(item);
                return true;
            }
        });

        uProfileBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // goes to the Profile Fragment
                profileFragment();
            }
        });

        searchBox.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // goes to the Search Box Fragment
                searchBoxResultsFragment();
            }
        });
    }

    private void profileFragment() {
        frag = ProfileFragment.newInstance("test1", "test2");
        if (frag != null) {
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            ft.add(R.id.fragmentContainer, frag, frag.getTag());
            ft.commit();
        }
    }

    private void searchBoxResultsFragment() {
        frag = SearchBoxFragment.newInstance("test1", "test2");
        if (frag != null) {
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            ft.add(R.id.fragmentContainer, frag, frag.getTag());
            ft.commit();
        }
    }

    // so it can be called from the adapter
    public void userFragment() {
        frag = UserFragment.newInstance("test1", "test2");
        if (frag != null) {
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            ft.replace(R.id.fragmentContainer, frag, frag.getTag());
            ft.commit();
        }
    }

    private void selectFragment(MenuItem item) {
        // init corresponding fragment
        switch (item.getItemId()) {
            case R.id.nav_home_btn:
                frag = HomeFragment.newInstance("test1", "test2");
                break;
            case R.id.nav_message_btn:
                frag = MessagesFragment.newInstance("test1", "test2");
                break;
            case R.id.nav_notif_btn:
                frag = NotificationsFragment.newInstance("test1", "test2");
                break;
            case R.id.nav_settings_btn:
                frag = SettingsFragment.newInstance("test1", "test2");
                break;
        }

        // uncheck the other items
        for (int i = 0; i< mBottomNav.getMenu().size(); i++) {
            MenuItem menuItem = mBottomNav.getMenu().getItem(i);
            menuItem.setChecked(menuItem.getItemId() == item.getItemId());
        }

        // sets the fragment to show
        if (frag != null) {
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            ft.add(R.id.fragmentContainer, frag, frag.getTag());
            ft.commit();
        }
    }
}

---

我将非常感谢任何帮助

您所做的错误是，您正在以编程方式在此行创建活动的新实例

mainNavHelper = new MainNavigation();

要解决此问题，您可以将

MainNavigation

实例传递到适配器并使用它

public class SearchResultsAdapter extends  RecyclerView.Adapter<SearchResultsAdapter.CustomViewHolder>{
    private List<User> users;

    Context context;

    public class CustomViewHolder extends RecyclerView.ViewHolder {
        public TextView userFN, userUN;

        public CustomViewHolder(View view) {
            super(view);
            userFN = (TextView) view.findViewById(R.id.userFullName);
            userUN = (TextView) view.findViewById(R.id.userUsername);

            // when userUN is clicked, then go to their profile
            userUN.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    userUN.setText("this text was clicked");
                    if (context instanceOf MainNavigation) {
                        ((MainNavigation) context).userFragment();
                    }
                }
            });
        }
    }

    public SearchResultsAdapter(Context context, List<User> users){
        this.context = context;        
        this.users = users;
    }

    @Override
    public SearchResultsAdapter.CustomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.users_list, parent, false);

        return new SearchResultsAdapter.CustomViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(SearchResultsAdapter.CustomViewHolder holder, int position) {
        User user = users.get(position);
        String uFN = user.getFirstName() + " " + user.getLastName();
        holder.userFN.setText(uFN);
        holder.userUN.setText(user.getUsername());
    }

    @Override
    public int getItemCount() {
        return users.size();
    }
}

公共类SearchResultAdapter扩展了RecyclerView.Adapter{
私人名单用户；
语境；
公共类CustomViewHolder扩展了RecyclerView.ViewHolder{
公共文本视图userFN，userUN；
公共CustomViewHolder（视图）{
超级（视图）；
userFN=（TextView）view.findViewById（R.id.userFullName）；
userUN=（TextView）view.findViewById（R.id.userUserUserName）；
//单击userUN后，转到其配置文件
userUN.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图v）{
userUN.setText（“单击了此文本”）；
if（主导航的上下文实例）{
（（主导航）context.userFragment（）；
}
}
});
}
}
公共SearchResultsAdapter（上下文、列表用户）{
this.context=上下文；
this.users=用户；
}
@凌驾
public SearchResultsAdapter.CustomViewHolder onCreateViewHolder（视图组父级，int-viewType）{
View itemView=LayoutInflater.from（parent.getContext（））
.充气（R.layout.users\u列表，父项，false）；
返回新的SearchResultsAdapter.CustomViewHolder（itemView）；
}
@凌驾
BindViewHolder上的公共无效（SearchResultsAdapter.CustomViewHolder，int位置）{
User=users.get（位置）；
字符串uFN=user.getFirstName（）+“”+user.getLastName（）；
holder.userFN.setText（uFN）；
holder.userUN.setText（user.getUsername（））；
}
@凌驾
public int getItemCount（）{
返回users.size（）；
}
}

您所做的错误在于，您正在此行以编程方式创建活动的新实例

mainNavHelper = new MainNavigation();

要解决此问题，您可以将

MainNavigation

实例传递到适配器并使用它

public class SearchResultsAdapter extends  RecyclerView.Adapter<SearchResultsAdapter.CustomViewHolder>{
    private List<User> users;

    Context context;

    public class CustomViewHolder extends RecyclerView.ViewHolder {
        public TextView userFN, userUN;

        public CustomViewHolder(View view) {
            super(view);
            userFN = (TextView) view.findViewById(R.id.userFullName);
            userUN = (TextView) view.findViewById(R.id.userUsername);

            // when userUN is clicked, then go to their profile
            userUN.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    userUN.setText("this text was clicked");
                    if (context instanceOf MainNavigation) {
                        ((MainNavigation) context).userFragment();
                    }
                }
            });
        }
    }

    public SearchResultsAdapter(Context context, List<User> users){
        this.context = context;        
        this.users = users;
    }

    @Override
    public SearchResultsAdapter.CustomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.users_list, parent, false);

        return new SearchResultsAdapter.CustomViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(SearchResultsAdapter.CustomViewHolder holder, int position) {
        User user = users.get(position);
        String uFN = user.getFirstName() + " " + user.getLastName();
        holder.userFN.setText(uFN);
        holder.userUN.setText(user.getUsername());
    }

    @Override
    public int getItemCount() {
        return users.size();
    }
}

公共类SearchResultAdapter扩展了RecyclerView.Adapter{
私人名单用户；
语境；
公共类CustomViewHolder扩展了RecyclerView.ViewHolder{
公共文本视图userFN，userUN；
公共CustomViewHolder（视图）{
超级（视图）；
userFN=（TextView）view.findViewById（R.id.userFullName）；
userUN=（TextView）view.findViewById（R.id.userUserUserName）；
//单击userUN后，转到其配置文件
userUN.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图v）{
userUN.setText（“单击了此文本”）；
if（主导航的上下文实例）{
（（主导航）context.userFragment（）；
}
}
});
}
}
公共SearchResultsAdapter（上下文、列表用户）{
this.context=上下文；
this.users=用户；
}
@凌驾
public SearchResultsAdapter.CustomViewHolder onCreateViewHolder（视图组父级，int-viewType）{
View itemView=LayoutInflater.from（parent.getContext（））
.充气（R.layout.users\u列表，父项，false）；
返回新的SearchResultsAdapter.CustomViewHolder（itemView）；
}
@凌驾
BindViewHolder上的公共无效（SearchResultsAdapter.CustomViewHolder，int位置）{
User=users.get（位置）；
字符串uFN=user.getFirstName（）+“”+user.getLastName（）；
holder.userFN.setText（uFN）；
holder.userUN.setText（user.getUsername（））；
}
@凌驾
public int getItemCount（）{
返回users.size（）；
}
}

mainNavHelper = new MainNavigation();

public class SearchResultsAdapter extends  RecyclerView.Adapter<SearchResultsAdapter.CustomViewHolder>{
    private List<User> users;

    Context context;

    public class CustomViewHolder extends RecyclerView.ViewHolder {
        public TextView userFN, userUN;

        public CustomViewHolder(View view) {
            super(view);
            userFN = (TextView) view.findViewById(R.id.userFullName);
            userUN = (TextView) view.findViewById(R.id.userUsername);

            // when userUN is clicked, then go to their profile
            userUN.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    userUN.setText("this text was clicked");
                    if (context instanceOf MainNavigation) {
                        ((MainNavigation) context).userFragment();
                    }
                }
            });
        }
    }

    public SearchResultsAdapter(Context context, List<User> users){
        this.context = context;        
        this.users = users;
    }

    @Override
    public SearchResultsAdapter.CustomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.users_list, parent, false);

        return new SearchResultsAdapter.CustomViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(SearchResultsAdapter.CustomViewHolder holder, int position) {
        User user = users.get(position);
        String uFN = user.getFirstName() + " " + user.getLastName();
        holder.userFN.setText(uFN);
        holder.userUN.setText(user.getUsername());
    }

    @Override
    public int getItemCount() {
        return users.size();
    }
}