如何等到藍牙在android中打開

Question

我需要以編程方式在 android 設備中打開藍牙，然后等到它打開以繼續執行下一行代碼。

我的代碼如下

if (!mBluetoothAdapter.isEnabled()) {
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                ctx.startActivity(enableBtIntent);
}

這樣做時，代碼從下一行繼續執行，而無需等待藍牙完全打開。 有沒有辦法解決這個問題？ 我可以添加一個外觀來檢查藍牙是否打開嗎？

Answer 1

您可以注冊一個BroadcastReceiver來監聽 BluetoothAdapter 上的狀態變化。

首先創建一個BroadcastReceiver來監聽狀態變化

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();

        if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {
            final int bluetoothState = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,
                                                BluetoothAdapter.ERROR);
            switch (bluetoothState) {
            case BluetoothAdapter.STATE_ON:
                //Bluethooth is on, now you can perform your tasks
                break;
            }
        }
    }
};

然后在創建時向您的Activity注冊BroadcastReceiver ，以便它可以開始接收事件。

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //Set a filter to only receive bluetooth state changed events.
    IntentFilter filter = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);
    registerReceiver(mReceiver, filter);
}

記住在Activity被銷毀時取消注冊偵聽器。

@Override
public void onDestroy() {
    super.onDestroy();
    unregisterReceiver(mReceiver);
}

Answer 2

您可以使用startActivityForResult()並在清單文件中使用藍牙權限檢查onActivityResult() resultCode是否為RESULT_OK ，例如..

mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (!mBluetoothAdapter.isEnabled()) {
    Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
    startActivityForResult(enableIntent, 0);
}

活動結果

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if(resultCode == RESULT_OK){
        // bluetooth enabled                      
    }else{
        // show error
    }       
}

ACTION_REQUEST_ENABLE

Answer 3

在您的清單文件上使用此代碼權限

<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>

和代碼

if (!mBluetoothAdapter.isEnabled()) {
     Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
     startActivityForResult(enableBtIntent , 0);
  } else
  {
     Toast.makeText(getApplicationContext(),"Already on", Toast.LENGTH_LONG).show();
  }

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(resultCode == RESULT_OK){
    Toast.makeText(getApplicationContext(),"Turned on",Toast.LENGTH_LONG).show();
}
if(resultCode == RESULT_CANCELED){

}

Answer 4

startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    //do your things
}