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文本视图。片段崩溃应用程序中的setText()

sensors fragment crash android

-1

hdw3 · 技术社区 · 7 年前

我正在努力改变 TextView 传感器上的内容更改,但在调用后 TextView.setText("foo"); 应用程序崩溃,就像 文本框 变量为null。我设置了 文本框 变量输入 onCreateView .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)
    {

    }
}

6 回复 | 直到 7 年前

AskNilesh 7 年前

首先,为布局充气

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

AskNilesh 7 年前

使用此

@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);
    }

IntelliJ Amiya 7 年前

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。首先在此处修改。

笔记

你会得到 NullPointerException 。

当应用程序在对象是必需的。

你应该通过 View's object 。

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;

Deep 7 年前

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) {

    }
}

Hitesh Sarsava 7 年前

把你的 findViewById 代码输入 onActivityCreated 如下所示:

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

NgoniDee 6 年前

有时,在片段中创建布局时,您会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。再次检查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,您的代码中没有太多细节(错误消息)