如何等到活动结果完成

Question

我有一个片段，如果用户不批准激活蓝牙，则不应打开该片段，这是通过这段代码请求

的

    Intent mIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
        mIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 240);
            startActivityForResult(mIntent, 1);
    //Here I want to exit the method in case result is denied
getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.content,new ServerFragment()).addToBackStack(null).commit();

我一直在很多地方寻找，我唯一发现的是使用来自新活动的 setResult（就我而言，onActivityResult 在调用活动中被覆盖，因为此代码位于片段中）

有什么想法吗？

谢谢！

编辑：这是一个堆栈跟踪

java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=131073, result=240, data=null} to activity {bt.bt/bt.bt.MainActivity}: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
                                                                               at android.app.ActivityThread.deliverResults(ActivityThread.java:3659)
                                                                               at android.app.ActivityThread.handleSendResult(ActivityThread.java:3702)
                                                                               at android.app.ActivityThread.access$1300(ActivityThread.java:155)
                                                                               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1366)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                               at android.os.Looper.loop(Looper.java:135)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:5343)
                                                                               at java.lang.reflect.Method.invoke(Native Method)
                                                                               at java.lang.reflect.Method.invoke(Method.java:372)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
                                                                            Caused by: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState

Answer 1

我认为你应该使用BroadcastReceiver来注册一个事件蓝牙。在清单.xml中，您需要添加两个语句：

<uses-permission android:name="android.permission.BLUETOOTH" />
<receiver android:name=".BluetoothBroadcastReceiver"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.bluetooth.adapter.action.STATE_CHANGED" />
 </intent-filter>
    </receiver>

然后你需要实现onReceive（）方法：

public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
    Log.d("BroadcastActions", "Action "+action+"received");
    int state;
    BluetoothDevice bluetoothDevice;
    switch(action)
    {
        case BluetoothAdapter.ACTION_STATE_CHANGED:
            state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1);
            if (state == BluetoothAdapter.STATE_OFF)
            {
                Toast.makeText(context, "Bluetooth is off", Toast.LENGTH_SHORT).show();
                Log.d("BroadcastActions", "Bluetooth is off");
            }
            else if (state == BluetoothAdapter.STATE_TURNING_OFF)
            {
                Toast.makeText(context, "Bluetooth is turning off", Toast.LENGTH_SHORT).show();
                Log.d("BroadcastActions", "Bluetooth is turning off");
            }
            else if(state == BluetoothAdapter.STATE_ON)
            {
getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.content,new ServerFragment()).addToBackStack(null).commit();
                Log.d("BroadcastActions", "Bluetooth is on");
            }
            break;
....
}

您可以在此链接中看到更多信息： Android广播接收器蓝牙事件捕获

Answer 2

您应该在启动意图后返回函数。然后，在 onActivityResult 中等待回调。在此方法中，如果结果RESULT_OK，则启动片段。

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == your_request_code_here) {
        if (resultCode != Activity.RESULT_CANCELED) {
            // start fragment
        }
    }
}

完整活动：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent mIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
                mIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 240);
                startActivityForResult(mIntent, 1);
            }
        });
    }
    @Override
    public void onPause() {
        super.onPause();
    }
    @Override
    public void onResume() {
        super.onResume();
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == 1) {
            if (resultCode != Activity.RESULT_CANCELED) {
            }
        }
    }
}

Answer 3

就像在您粘贴的代码中一样，您在调用startActivityForResult()后立即实例化片段，您不需要这样做 - 这会导致问题。您只需要startActivityForResult()，然后在活动中的onActivityResult()方法中，如果结果代码RESULT_OK，则可以实例化您的片段

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == your_request_code_here) {
        if (resultCode == Activity.RESULT_OK) {
getSupportFragmentManager().beginTransaction().replace(R.id.content,new ServerFragment()).addToBackStack(null).commit();
        }
    }
}