从活动到当前加载的片段的接口不起作用

Question

我想在单击按钮时将数据从 Activity 传递到当前加载的片段。 为此，我创建了接口并定义为活动并在接口中实现，但无法在片段中获得响应。

每当按钮在 Activity 中触发时，我都需要输出。

这是我的代码。请帮我解决这个问题。

界面

public interface Click {
    void onClick(String msg);
}

主要活动

public class MainActivity extends FragmentActivity {
    DrawerLayout dlMain;
    Button btnClick;

    Click click;

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


        FragmentOne fragmentOne = new FragmentOne();
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.flContainer, fragmentOne,"FragmentOne");
        ft.commit();

        click = (Click) getSupportFragmentManager().findFragmentByTag("FragmentOne").;

        dlMain = (DrawerLayout) findViewById(R.id.dlMain);
        btnClick = (Button) findViewById(R.id.btnClick);

        btnClick.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.e("Btn Click", "click");
                click.onClick("Button Clicked!");
            }
        });
    }
}

FragmentOne

public class FragmentOne extends Fragment implements Click {
   @Nullable
   @Override
   public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
       View view = inflater.inflate(R.layout.fragment_one, container, false);
       return view;
   }

   @Override
   public void onClick(String msg) {
       Toast.makeText(getActivity(), msg, Toast.LENGTH_SHORT).show();
   }
}

但是我在 MainActivity 中遇到错误 这是我的错误日志。

05-09 10:30:49.092 19101-19101/com.psk.interfacetest E/Btn 点击：点击 05-09 10:30:49.095 19101-19101/com.psk.interfacetest E/AndroidRuntime: 致命异常: main 进程：com.psk.interfacetest，PID：19101 java.lang.NullPointerException 在 com.psk.interfacetest.MainActivity$1.onClick(MainActivity.java:37) 在 android.view.View.performClick(View.java:4471) 在 android.view.View$PerformClick.run(View.java:18778) 在 android.os.Handler.handleCallback(Handler.java:808) 在 android.os.Handler.dispatchMessage(Handler.java:103) 在 android.os.Looper.loop(Looper.java:193) 在 android.app.ActivityThread.main(ActivityThread.java:5345) 在 java.lang.reflect.Method.invokeNative(Native Method) 在 java.lang.reflect.Method.invoke(Method.java:515) 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640) 在 dalvik.system.NativeStart.main(Native Method)

Answer 1

您的情况，片段替换无法完成。所以你应该从fragment注册接口。你可以检查这个代码。

      public class AActivity extends FragmentActivity {
            Click click;
            @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);
 FragmentOne fragmentOne = new FragmentOne();
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.flContainer, fragmentOne,"FragmentOne");
        ft.commit();
              DrawerLayout dlMain = (DrawerLayout)findViewById(R.id.dlMain);
            Button    btnClick = (Button) findViewById(R.id.btnClick);

                btnClick.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Log.e("Btn Click", "click");
                        click.onClick("Button Clicked!");
                    }
                });
            }

            public void setCallback(Click callback) {
                this.click=callback;
            }
            public interface Click {
                void onClick(String msg);
            }
        }

        public class AFragment extends Fragment implements AActivity.Click {
            @Override
            public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
                super.onViewCreated(view, savedInstanceState);
                if (getActivity() != null) {
                    ((AActivity)getActivity()).setCallback(this);
                }
            }

            @Override
            public void onClick(String msg) {

            }
        }

Answer 2

try this



public class MainActivity extends FragmentActivity {
    DrawerLayout dlMain;
    Button btnClick;

    Click click;
    private FragmentOne fragmentOne;

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


         fragmentOne = new FragmentOne();
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.imageTitleTextView, fragmentOne, "FragmentOne");
        ft.commit();

        //click = (Click) getSupportFragmentManager().findFragmentByTag("FragmentOne");

    dlMain = (DrawerLayout) findViewById(R.id.dlMain);
        btnClick = (Button) findViewById(R.id.btnClick);

        btnClick.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.e("Btn Click", "click");
                fragmentOne.listener.onClick("Button Clicked!");
            }
        });
    }
}


public class FragmentOne extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_one, container, false);
        return view;
    }
Click listener = new Click() {
    @Override
    public void onClick(String msg) {
        Toast.makeText(getActivity(), msg, Toast.LENGTH_SHORT).show();
    }
};

}