android遇到的问题的总结----Activity和fragment之间相互跳转

一、activity与activity之间跳转：

//第一个参数是上下文,
//第二个参数是将要跳转的activity
  Intent intent = new Intent(LoginActivity.this,StudentActivity.class);
 startActivity(intent);
//带参数跳转：
 Intent intent = new Intent(LoginActivity.this,StudentActivity.class);
intent.putExtra("Flag",flag);
startActivity(intent);

//另一个activity通过：
 getIntent().getIntExtra("Flag", 0);
 或
  getIntent().getStringExtra("Flag");
 

二、activity跳转fragment：

activity不能直接跳转到fragment,必须先跳转到fragment对应的activity中
法一：
activity可通过发送广播

  show_pick_course.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v) {
                T_pick_course.this.finish();
                Log.v("qjm", "show_pick_course click");
                Intent intent = new Intent("android.intent.action.CART_BROADCAST");
                intent.putExtra("data", "refresh");
                LocalBroadcastManager.getInstance(T_pick_course.this).sendBroadcast(intent);
                sendBroadcast(intent);

            }
        });

fragment接收广播：

 @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
      //  Log.v("qjm","show_pick_course click onActivityCreated");
        LocalBroadcastManager broadcastManager=LocalBroadcastManager.getInstance(getActivity());
        IntentFilter intentFilter=new IntentFilter();
        intentFilter.addAction("android.intent.action.CART_BROADCAST");
        BroadcastReceiver broadcastReceiver=new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                String msg=intent.getStringExtra("data");
                if("refresh".equals(msg)){
                //执行的操作
                }
         }
       };
        broadcastManager.registerReceiver(broadcastReceiver,intentFilter);
    }

法二：
Activity:
通过setReult("请求码")

 btn_back.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //返回查看课表
                setResult(222);
            }
        });

fragment:重写onActivityResult（）方法，activity传来的请求码，标记要跳转到哪个fragment。例如222，跳转到的是CourseFragment

 @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode==1&&resultCode==222){//pan段响应码和请求码
            StudentActivity studentActivity=(StudentActivity)getActivity();
            android.support.v4.app.FragmentManager fragmentManager=studentActivity.getSupportFragmentManager();
            android.support.v4.app.FragmentTransaction fragmentTransaction=fragmentManager.beginTransaction();
            fragmentTransaction.replace(R.id.rb_course, new CourseFragment());
            fragmentTransaction.commit();
        }
    }

二、fragment跳转activity：

//mContext指代上下文，可以换成getActivity()
 Intent intent=new Intent(mContext,T_pick_course.class);
   startActivity(intent);

再添加一个知识点：

返回上一个页面：调用.finish();

finish()：用于结束一个activity的生命周期，finish是activity类，针对activity,当调用finish()后，仅仅把当前activity推向后台，并没有释放资源。

//从activity1--->activity2
Intent intent=new Intent(activity1.this,activity2.class);
startActivity(intent);
finish();