Android 应用程序中的TextView.setText（）

我试图更改传感器更改上的

TextView

内容，但调用

TextView.setText（“foo”）应用程序崩溃，就像
TextView
变量为空一样。我在
onCreateView
中设置了
TextView
变量。代码如下：

public class fragment1 extends Fragment implements SensorEventListener
{
    private SensorManager mSrMgr = null;
    private Sensor mLight;
    private TextView page1;
    protected View mView;


    public fragment1()
    {
        // Required empty public constructor
    }

    public void onCreate(Bundle savedInstance)
    {
        super.onCreate(savedInstance);
        mSrMgr = (SensorManager) getActivity().getSystemService(SENSOR_SERVICE);
        mLight = mSrMgr.getDefaultSensor(Sensor.TYPE_LIGHT);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState)
    {
        page1 = container.findViewById(R.id.page1);
        View view = inflater.inflate(R.layout.fragment_fragment1, container, false);
        this.mView = view;
        return inflater.inflate(R.layout.fragment_fragment1, container, false);
    }

    public void onPause()
    {
        super.onPause();
        this.unregister();
    }

    public void onResume()
    {
        super.onResume();
        this.registerSensorListiner();
    }

    private void registerSensorListiner()
    {
        mSrMgr.registerListener(this, mLight, SensorManager.SENSOR_DELAY_NORMAL);
    }

    private void unregister()
    {
        mSrMgr.unregisterListener(this);
    }


    @Override
    public void onSensorChanged(SensorEvent event)
    {
        Toast.makeText(getContext(),String.valueOf(event.values[0]),Toast.LENGTH_SHORT).show();
        page1.setText("elo"); //here is the crashing part
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy)
    {

    }
}

用这个

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState)
{            
   View view = inflater.inflate(R.layout.fragment_fragment1, container, false);
   this.mView = view;
   page1 = view.findViewById(R.id.page1);
   return view;
}

而不是这个

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState)
    {
        page1 = container.findViewById(R.id.page1);
        View view = inflater.inflate(R.layout.fragment_fragment1, container, false);
        this.mView = view;
        return inflater.inflate(R.layout.fragment_fragment1, container, false);
    }

为什么多次
R.layout.

  View view = inflater.inflate(R.layout.fragment_fragment1, container, false);
        this.mView = view;
        return inflater.inflate(R.layout.fragment_fragment1, container, false);

应该是一次。首先在这里修改

注意

你会得到的

当应用程序试图在
对象是必需的

您应该传递视图的对象

page1 = view.findViewById(R.id.page1);

最后

 View view = inflater.inflate(R.layout.fragment_fragment1, container, false);
 page1 = view.findViewById(R.id.page1);
 this.mView = view;
 return view;

首先，膨胀布局

View view = inflater.inflate(R.layout.fragment_fragment1, container, false);
this.mView = view;
page1 = view.findViewById(R.id.page1); 
return view, false);

使用
view
对象调用findViewById方法
将您的
findViewById
代码放入创建的
活动中
，如下所示：

public class fragment1 extends Fragment implements SensorEventListener {
    private SensorManager mSrMgr = null;
    private Sensor mLight;
    private TextView page1;
    protected View mView;


    public fragment1() {
        // Required empty public constructor
    }

    public void onCreate(Bundle savedInstance) {
        super.onCreate(savedInstance);
        mSrMgr = (SensorManager) getActivity().getSystemService(SENSOR_SERVICE);
        mLight = mSrMgr.getDefaultSensor(Sensor.TYPE_LIGHT);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        mView = inflater.inflate(R.layout.fragment_fragment1, container, false);
        page1 = mView.findViewById(R.id.page1);
        return mView;
    }

    public void onPause() {
        super.onPause();
        this.unregister();
    }

    public void onResume() {
        super.onResume();
        this.registerSensorListiner();
    }

    private void registerSensorListiner() {
        mSrMgr.registerListener(this, mLight, SensorManager.SENSOR_DELAY_NORMAL);
    }

    private void unregister() {
        mSrMgr.unregisterListener(this);
    }


    @Override
    public void onSensorChanged(SensorEvent event) {
        Toast.makeText(getContext(), String.valueOf(event.values[0]), Toast.LENGTH_SHORT).show();
        page1.setText("elo"); //here is the crashing part
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {

    }
}

 @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        page1 = getActivity().findViewById(R.id.page1);
    }

有时，在片段中创建布局时，复制并粘贴具有重复ID的xml代码。然后，当您调用粘贴资源的id时，它将尝试调用第一个定义的资源，该资源在运行时可能为null。仔细检查page1 id是否仅在一个片段的Xml中找到。如果不解决“findviewbyid”。我希望这会有所帮助，代码中有一些细节（错误消息）
崩溃日志（如果有）？你是对的，只是实验中留下了一些混乱，谢谢注意。@hdw3确实如此。感谢您的回复。欢迎，您可以接受答案，也可以填写：-）快乐编码