接口无法从活动到当前加载的片段

时间：2016-05-09 05:09:41

标签： android android-fragments interface android-fragmentactivity

我想在按钮点击时将数据从Activity传递到当前加载的片段。为此，我创建了Interface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中点击时，我都需要输出。

这是我的代码。请帮我解决这个问题。

Inteface

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：FATAL EXCEPTION：main 过程：com.psk.interfacetest，PID：19101 显示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） at 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（本地方法）

2 个答案:

答案 0 :(得分：1)

你的情况下，片段替换无法完成。所以你应该从fragment注册接口。你可以检查这段代码。

      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) {

            }
        }

答案 1 :(得分：1)

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();
    }
};

}