Question

我已经创建了用于检测otg电缆的应用程序。当我启动它时显示“otg not connected”并且它重复多次，当我插入otg电缆时它仍然重复“otg not connected”并且在一段时间后它显示“ otg连接“!!!!

当我启动应用程序时，它不应该显示任何内容，它应该仅在我插入或插入otg cable时显示。并且它不应该多次重复相同的消息!!!!

MainActivity.class

public class MainActivity extends AppCompatActivity
{
    private Process suProcess;
    private PendingIntent pendingIntent;

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

        getRoot();
        startAlarm();
    }

    private void getRoot()
    {
        try
        {
            suProcess = Runtime.getRuntime().exec("su");
        }
        catch (IOException e)
        {

        }
    }

    private void startAlarm()
    {
        Intent alarmIntent = new Intent(MainActivity.this, AlarmReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, alarmIntent, 0);

        AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        int interval = 1000;
        manager.setInexactRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), interval, pendingIntent);
    }
}

AlarmReceiver.class

public class AlarmReceiver extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context,Intent intent)
    {
        File directory = new File("/sys/bus/usb/devices");
        File[] contents = directory.listFiles();

        if(contents.length == 0)
        {
            Toast.makeText(context,"otg not connected",Toast.LENGTH_SHORT).show();
        }
        else
        {
            Toast.makeText(context,"otg connected",Toast.LENGTH_SHORT).show();
        }
    }
}

Answer 1

如果您不想在appstart上发出警报，请不要将其放在onCreate方法中。我会把这个方法放在一个Runnable中，这个方法会调用startalarm。在AlarmReceiver类中会添加一个静态int

private static int conn_length = 0;

并在onReceive方法中，如果要生成以下代码：

File directory = new File("/sys/bus/usb/devices");
File[] contents = directory.listFiles();

if(contents.length == conn_length){
    return;
}
else{
    conn_length = contents.length;
}

if(conn_length == 0)
{
    Toast.makeText(context,"otg not connected",Toast.LENGTH_SHORT).show();
}
else
{
    Toast.makeText(context,"otg connected",Toast.LENGTH_SHORT).show();
}

这样，如果连接状态发生变化，您只能获得一条消息。

编辑：

Runnable实现的示例。

在onCreate方法中添加此

Handler handler = new Handler();
handler.post(alarmUpdater);

在课堂的另一部分：

public Runnable alarmUpdater= new Runnable() {
    @Override
    public void run() {
        startalarm();
    }
};

Android Alarm Manager重复

1 个答案: