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Kevtho
Asked: 2020-01-06 07:43:22 +0800 CST 2020-01-06 07:43:22 +0800 CST

Android app pre-close event

  • 772

In an application I have a main activity and several fragments, the application works by connecting to two bluetooth devices.

What I need is that before closing THE APPLICATION disconnect and turn off the bluetooth of the mobile. I have tried with the onDestoy() and onPause() methods inside the MainActivity but I don't have the expected results because although the blue turns off the application becomes unstable and exceptions are generated and it cannot exit normally.

Can someone guide me with the method on which I should program. Thank you very much.

@Override
public void onDestroy(){
    super.onDestroy();
    try {
        mBluetoothAdapter.disable();
        mBluetoothGatt.disconnect();
    } catch (Exception ex) {
    }
}

I emphasize the problem is not the lines of code, because if they turn off the bluetooth, but it is the event within which I do it that generates unwanted exceptions.

android

2 Answers

  1. Best Answer

    Check out this answer from @BradHein , you should first close the streams and open connections and then the BluetoothAdapter/BluetoothManager :

    @Override
public void onDestroy(){
    super.onDestroy();
    try {
        resetConnection();
        if (mBluetoothAdapter.isEnabled()) { //comprueba esta habilitado.
              mBluetoothAdapter.disable(); //Deshabilita.
        }
        //mBluetoothGatt.disconnect();
    } catch (Exception ex) {
    }
}

    method resetConnection():

    private void resetConnection() {
        if (mBTInputStream != null) {
                try {mBTInputStream.close();} catch (Exception e) {}
                mBTInputStream = null;
        }

        if (mBTOutputStream != null) {
                try {mBTOutputStream.close();} catch (Exception e) {}
                mBTOutputStream = null;
        }

        if (mBTSocket != null) {
                try {mBTSocket.close();} catch (Exception e) {}
                mBTSocket = null;
        }

}

    Check the life cycle of the Activity:

    enter image description here

    • 4

  2. Which method you should choose depends on the behavior you are expecting from your application. If you want to disable Bluetooth when another application is brought to the foreground (the user switches tasks, for example), you should use the onResume()and methods onPause().

    Lifecycle of an Activity

    If you want to disable BT when your app is completely destroyed, then onDestroy().

    Regarding the errors that you are receiving, I suggest that you apply the following criteria when calling the methods of the class super.

    • When you override a method that creates your application (onCreate, onResume, etc.) you should call the parent class method first (with super.onResume()).

    • When you override a method that destroys your app (onDestroy, onPause, etc.), call the parent class's method last ( super.onPause())

    I give you an example:

    @Override
public void onResume()
{
    // Primero llamo al sistema 
    super.onResume();

    // Aquí hago mi trabajo
}

@Override
public void onPause()
{
    // Aquí libero mis recursos, 
    // En concreto desactivo el Bluetooth

    // Y ahora llamo a la clase padre
    super.onPause();
}

    Please take this as a general rule, as there are always exceptions.

    • 1