Activity之间通信

• Intent / Bundle
• 类静态变量
• 全局变量

Activity与Fragment通信

• Activity将数据传递给Fragment

  • 通过Bundle

  public class FragmentActivity1 extends Activity {
      public String productId;
  
      @Override
      protected void onCreate(@Nullable Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          Bundle bundle = new Bundle();
          bundle.putString(Constant.INTENT_ID, productId);
          Fragment fragment = new Fragment1();
          fragment.setArguments(bundle);
      }
  }
  

  public class Fragment1 extends Fragment {
      public String productId;
  
      @Override
      public void onStart() {
          super.onStart();
          if (isAdded()) {//判断Fragment已经依附Activity
              productId = getArguments().getString(Constant.INTENT_ID);
          }
      }
  }
  

  • 在Activity中定义方法

  public class FragmentActivity2 extends Activity {
      @Override
      protected void onCreate(@Nullable Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
      }
  
      public String getTitles(){
          return "getTitle";
      }
  }
  

  public class Fragment2 extends Fragment {
      public String titles;
      @Override
      public void onAttach(Context context) {
          super.onAttach(context);
          titles = ((FragmentActivity2) context).getTitles();//通过强转成宿主activity，就可以获取到传递过来的数据
      }
  }
  

• Fragment将数据传递给Activity

  1.在Fragment中定义一个内部接口回调
  2.Activity实现该接口回调
  3.在Fragment的OnAttach()中获得实现了该接口的Activity
  4.在Fragment的OnDetach()中把传递进来的Activity对象释放掉

  public class Fragment3 extends Fragment implements View.OnClickListener {
      // 2.1 定义用来与外部activity交互，获取到宿主activity
      private FragmentListener listener;
  
      // 1 定义了所有activity必须实现的接口方法
      public interface FragmentListener {
          void process(String str);
      }
  
      // 当Fragment被加载到activity的时候会被回调
      @Override
      public void onAttach(Activity activity) {
          super.onAttach(activity);
  
          if(activity instanceof FragmentListener) {
              listener = (FragmentListener)activity; // 2.2 获取到宿主activity并赋值
          } else{
              throw new IllegalArgumentException("activity must implements FragmentListener");
          }
      }
  
      @Override
      public void onClick(View v) {
          listener.process("我是接口"); //3.1 执行回调
      }
  
      //把传递进来的activity对象释放掉
      @Override
      public void onDetach() {
          super.onDetach();
          listener = null;
      }
  }
  

  public class FragmentActivity3 extends Activity implements Fragment3.FragmentListener {
      @Override
      public void process(String str) {
          //todo
      }
  }