java - 我如何获取 fragment 以将 onClickListener 结果发送回主要 Activity

Question

我有一个 Main Activity ，它在第一次启动时显示一个 fragment ，该 fragment 显示已配对蓝牙设备的 ListView 。我不想使用 ListFragment，因为我想在顶部显示 TextView。 我创建了一个 onItemClickListener，它使用所选设备的 MAC 地址和名称设置字符串。这在日志中显示正常 我想将这些字符串发送回主要 Activity ，然后打开一个使用这些字符串连接到蓝牙设备的不同 fragment 。

我已经使用所有 Activity 完成了这项工作，但我想更改为 Fragments。

我的主要 Activity 是。

 import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;


public class MainActivity extends AppCompatActivity {

    // MAC-address of Bluetooth module (you must edit this line)
    private static String address = "No Device Selected";
    private static String itemName = "No Device Selected";

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

}

布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <fragment
        class="com.ming.pondcontroller.AddressFragment"
        android:id="@+id/main_frag"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

我的地址 fragment

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.Intent;
import android.os.Bundle;
import android.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Set;

public class AddressFragment extends Fragment {

    private static final String TAG = "get address Activity";
    private BluetoothAdapter BA = null;
    private Set<BluetoothDevice> pairedDevices;
    LayoutInflater inflater2;
    ListView lv;
    String address;
    String itemName;
    String itemString;

    public AddressFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        inflater2 = inflater;
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_address, container, false);
    }

    @Override
    public void onStart(){
        super.onStart();
        lv = (ListView)getView().findViewById(R.id.listView);
        BA = BluetoothAdapter.getDefaultAdapter();
        checkBTState();

        // get paired devices
        pairedDevices = BA.getBondedDevices();
        ArrayList list = new ArrayList();
        // get a list of paired devices
        for(BluetoothDevice bt:pairedDevices){
            list.add(bt.getName()+"\n"+bt.getAddress());
        }
        // display the list in the list view
        final ArrayAdapter adapter = new ArrayAdapter(inflater2.getContext(),android.R.layout.simple_list_item_1,list);
        lv.setAdapter(adapter);

        // onItemClick Listener
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?> adapterView,View view, int position, long l){
                // get the text of the item clicked from position
                itemString = (String)(lv.getItemAtPosition(position));
                // get last 17 characters for MAC address
                address = itemString.substring(itemString.length()-17);
                itemName = itemString.substring(0,itemString.length()-17);
                Log.d(TAG,address);

            }
        }); //end of onClickListener
    }

    private void checkBTState() {
        // Check for Bluetooth support and then check to make sure it is turned on
        // Emulator doesn't support Bluetooth and will return null
        if(BA==null) {
            Log.d("Fatal Error", "Bluetooth not support");
        } else {
            if (BA.isEnabled()) {
                Log.d(TAG, "...Bluetooth ON...");
            } else {
                //Prompt user to turn on Bluetooth
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, 1);
            }
        }
    }
}

及其布局。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorMainBack"
    tools:context="com.ming.pondcontroller.AddressFragment">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:id="@+id/textView"
        android:background="@color/colorPrimary"
        android:textColor="@color/colorWhite"
        android:textSize="20dp"
        android:text="Select Device"/>
    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/textView"
        android:background="@color/colorTextBack">
    </ListView> />
</RelativeLayout>

我查看了大量回调、监听器和接口(interface)的示例，但似乎无法在不使用 listFragment 的情况下找到正确的东西。

Answer 1

创建一个您的 Activity 将实现的接口(interface)，然后在 onAttach() 中将其设置为您的 Fragment 中的成员变量:

接口(interface)类:

interface BluetoothItemSelected {
    void onBluetoothItemSelected(String itemName, String itemAddress);
}

MainActivity 实现:

public class MainActivity extends AppCompatActivity implements BluetoothItemSelected {

    // MAC-address of Bluetooth module (you must edit this line)
    private static String address = "No Device Selected";
    private static String itemName = "No Device Selected";

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

    @Override
    public void onBluetoothItemSelected(String itemName, String itemAddress) {
        // TODO do your work here
    }

    // your other Activity code...

}

fragment 实现:

public class AddressFragment extends Fragment {

    private static final String TAG = "get address Activity";
    private BluetoothAdapter BA = null;
    private Set<BluetoothDevice> pairedDevices;
    LayoutInflater inflater2;
    ListView lv;
    String address;
    String itemName;
    String itemString;

    BluetoothItemListener btItemListener;

    @Override
    public void onAttach(Context activity) {
        if (activity instanceof BluetoothItemListener) {
            btItemListener = (BluetoothItemListener) activity;
        }
    }

    @Override
    public void onDetach() {
        // remove the reference to your Activity
        btItemListener = null;
    }



    @Override
    public void onStart(){
        super.onStart();
        lv = (ListView)getView().findViewById(R.id.listView);
        BA = BluetoothAdapter.getDefaultAdapter();
        checkBTState();

        // get paired devices
        pairedDevices = BA.getBondedDevices();
        ArrayList list = new ArrayList();
        // get a list of paired devices
        for(BluetoothDevice bt:pairedDevices){
            list.add(bt.getName()+"\n"+bt.getAddress());
        }
        // display the list in the list view
        final ArrayAdapter adapter = new ArrayAdapter(inflater2.getContext(),android.R.layout.simple_list_item_1,list);
        lv.setAdapter(adapter);

        // onItemClick Listener
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?> adapterView,View view, int position, long l){
                // get the text of the item clicked from position
                itemString = (String)(lv.getItemAtPosition(position));
                // get last 17 characters for MAC address
                address = itemString.substring(itemString.length()-17);
                itemName = itemString.substring(0,itemString.length()-17);
                Log.d(TAG,address);
                // call your interface here
                if (btItemListener != null) {
                    btItemListener.onBluetoothItemSelected(itemName, address);
                }
            }
        }); //end of onClickListener
    }

    // your other Fragment code ...
}