为什么我无法在另一个类方法上初始化蓝牙

Question

这是我最近发布的一个后续场景，我尝试从另一个类调用一个方法并以更改 TextView 来响应。现在我正在尝试添加以在该方法（BluetoothOn）上初始化蓝牙适配器，但是，我再次面临与应用程序停止相同的错误。另一方面，如果我在 Main 方法上声明 BLEadapter，我可以毫无问题地运行应用程序。

public class MainActivity extends Activity {

    private BluetoothAdapter mBluetoothAdapter;
    private static final int REQUEST_ENABLE_BT = 1;

        private TextView textView;
        //private View myView;
        Button button;

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

                textView =(TextView)findViewById(R.id.textView1);
                addListenerOnButton();
            }

            private void addListenerOnButton() {
                button = (Button) findViewById(R.id.button1);

                button.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View arg0) {

                        enableBluetooth(arg0);
                    }

                });
            }

            @Override
            public boolean onCreateOptionsMenu(Menu menu) {
                // Inflate the menu; this adds items to the action bar if it is present.
                getMenuInflater().inflate(R.menu.main, menu);
                return true;
            }

            @Override
            public boolean onOptionsItemSelected(MenuItem item) {
                // Handle action bar item clicks here. The action bar will
                // automatically handle clicks on the Home/Up button, so long
                // as you specify a parent activity in AndroidManifest.xml.
                int id = item.getItemId();
                if (id == R.id.action_settings) {
                    return true;
                }
                return super.onOptionsItemSelected(item);
            }

            public void enableBluetooth (View view){     

            BluetoothOn ble = new BluetoothOn();
            ble.initializeBlue(textView);



            }       
}

在我的蓝牙课上

    public class BluetoothOn extends MainActivity {  

        private TextView textView1;

        private BluetoothAdapter mBluetoothAdapter;
        private static final int REQUEST_ENABLE_BT = 1;

        public void initializeBlue(View myView){

            String BleisOn = "Bluetooth enabled !!!!";

            textView1 = (TextView)myView.findViewById(R.id.textView1);
            textView1.setText(BleisOn);


            // Initializes Bluetooth adapter.
            final BluetoothManager bluetoothManager =
            (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
            mBluetoothAdapter = bluetoothManager.getAdapter();

            // Ensures Bluetooth is available on the device and it is enabled. If not,
            // displays a dialog requesting user permission to enable Bluetooth.
            if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
                        }
        }

}

谁能告诉我如何从我的主要活动中调用不会导致应用程序崩溃的方法。我只是一个初学者，请详细解释一下，我需要什么东西，我只想在 main 之外创建其他类，并在用户在 Android 应用程序上进行交互时调用这些方法。我认为我只是没有正确地将值传递给其他类，这就是为什么它在 android 上不起作用......一旦我点击分配的按钮，应用程序就会崩溃。这段代码我需要什么。顺便说一下，这是我之前帖子中的链接，creating a separate class without a user interface 请帮助谢谢各位好人...

这是日志猫

09-01 13:26:27.307: I/ActivityManager(19336): Timeline: Activity_idle id: android.os.BinderProxy@42d54610 time:341763403
09-01 13:26:39.627: D/AndroidRuntime(21289): Shutting down VM
09-01 13:26:39.627: W/dalvikvm(21289): threadid=1: thread exiting with uncaught exception (group=0x4156cd88)
09-01 13:26:39.627: E/AndroidRuntime(21289): FATAL EXCEPTION: main
09-01 13:26:39.627: E/AndroidRuntime(21289): Process: com.example.thisapp, PID: 21289
09-01 13:26:39.627: E/AndroidRuntime(21289): java.lang.IllegalStateException: System services not available to Activities before onCreate()
09-01 13:26:39.627: E/AndroidRuntime(21289):    at android.app.Activity.getSystemService(Activity.java:4532)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at com.example.thisapp.BluetoothOn.initializeBlue(BluetoothOn.java:27)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at com.example.thisapp.MainActivity.enableBluetooth(MainActivity.java:71)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at com.example.thisapp.MainActivity$1.onClick(MainActivity.java:43)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at android.view.View.performClick(View.java:4569)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at android.view.View$PerformClick.run(View.java:18553)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at android.os.Handler.handleCallback(Handler.java:733)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at android.os.Handler.dispatchMessage(Handler.java:95)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at android.os.Looper.loop(Looper.java:212)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at android.app.ActivityThread.main(ActivityThread.java:5151)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at java.lang.reflect.Method.invokeNative(Native Method)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at java.lang.reflect.Method.invoke(Method.java:515)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:877)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
09-01 13:26:39.627: E/AndroidRuntime(21289):    at dalvik.system.NativeStart.main(Native Method)
09-01 13:26:41.487: I/Process(21289): Sending signal. PID: 21289 SIG: 9

Answer 1

您的代码存在一些问题：

1. BluetoothOn 不应该有extends MainActivity。

2. BluetoothOn 不应该知道任何 UI 组件。将View 传递给initializeBlue() 方法是一个糟糕的设计决策。有关如何将 UI 逻辑与蓝牙逻辑分开的建议，请参阅 this answer 到您之前的问题。