java - fragment 中的addView()框架布局

我试图在FrameLayout片段中查看相机。但是，我得到了java.lang.NullPointerException。这是片段代码：

public class ScanFragment extends Fragment {

public ScanFragment(){}

 private Camera mCamera;
 private CameraPreview mPreview;
 private Handler autoFocusHandler;
 private static final String TAG_PID = "pid";

 TextView scanText;
 ImageScanner scanner;
 private boolean barcodeScanned = false;
 private boolean previewing = true;


 static {
     System.loadLibrary("iconv");
 }

public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);

}


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

    View rootView = inflater.inflate(R.layout.fragment_home, container, false);
    autoFocusHandler = new Handler();
    mCamera = getCameraInstance();

    /* Instance barcode scanner */
    scanner = new ImageScanner();
    scanner.setConfig(0, Config.X_DENSITY, 3);
    scanner.setConfig(0, Config.Y_DENSITY, 3);

    mPreview = new CameraPreview(this.getActivity(), mCamera, previewCb, autoFocusCB);
    FrameLayout preview = (FrameLayout) rootView.findViewById(R.id.cameraPreview);
    preview.addView(mPreview);

    scanText = (TextView) rootView.findViewById(R.id.scanText);
    return rootView;
}
// create object CameraPriew
mPreview = new CameraPreview(this.getActivity(), mCamera, previewCb, autoFocusCB);
FrameLayout preview = (FrameLayout) rootView.findViewById(R.id.cameraPreview);
// View Camera in FrameLayout of the fragment
preview.addView(mPreview);

这是片段的布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">

<FrameLayout
    android:id="@+id/cameraPreview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="1"
    />

<TextView
    android:id="@+id/scanText"
    android:text=""
    android:layout_height="wrap_content"
    android:layout_width="match_parent">
</TextView>
</LinearLayout>

这是CameraPreview类：

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
private PreviewCallback previewCallback;
private AutoFocusCallback autoFocusCallback;

public CameraPreview(Context scanFragment, Camera camera,
                     PreviewCallback previewCb,
                     AutoFocusCallback autoFocusCb) {
    super(scanFragment);
    mCamera = camera;
    previewCallback = previewCb;
    autoFocusCallback = autoFocusCb;


    // Install a SurfaceHolder.Callback so we get notified when the
    // underlying surface is created and destroyed.
    mHolder = getHolder();
    mHolder.addCallback(this);

    // deprecated setting, but required on Android versions prior to 3.0
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}

我很确定Fragment中没有addView（）。我该如何解决。谢谢

最佳答案

解决了：

在ScanFragment类上，我调用了正确的布局。 addView（）方法不是这里的罪魁祸首。

public class ScanFragment extends Fragment {

public ScanFragment(){}

 private Camera mCamera;
 private CameraPreview mPreview;
 private Handler autoFocusHandler;
 private static final String TAG_PID = "pid";

 TextView scanText;
 ImageScanner scanner;
 private boolean barcodeScanned = false;
 private boolean previewing = true;
 FrameLayout preview;

 static {
     System.loadLibrary("iconv");
 }

public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
}

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

    // previously fragment_home
    View rootView = inflater.inflate(R.layout.fragment_scan, container, false);
    autoFocusHandler = new Handler();
    mCamera = getCameraInstance();
     mPreview = new CameraPreview(this.getActivity(), mCamera, previewCb, autoFocusCB);
    preview = (FrameLayout) rootView.findViewById(R.id.cameraPreview);
    preview.addView(mPreview);

    scanText = (TextView) rootView.findViewById(R.id.scanText);
    return rootView;
}

而且我忘了在android清单中添加Camera Permission。

<uses-permission android:name="android.permission.CAMERA"/>