调用Activity onResume后，ViewPager中的FrameLayout膨胀

Question

Okay so I am using a ViewPager in my app and I would like to add a Camera Preview to the last page in the ViewPager. I am facing some issues because in order to start the preview I am assigning it to a FrameLayout within the last page of my ViewPager. For some reason however the ViewPager doesn't inflate its pages until after the entire onCreate() and onResume() methods are called. This is problematic because when I try to find the FrameLayout by ID it returns null since that page hasn't been inflated yet. Is there anyway I can fix this?

Here is the code for the camerapreview. I had an if check to see if my preview was null and it is.

package me.bionicsheep.aegis;

import com.qualcomm.snapdragon.sdk.face.FacialProcessing;

import android.os.Bundle;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.hardware.Camera.PreviewCallback;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.Display;
import android.view.Surface;
import android.view.WindowManager;
import android.widget.FrameLayout;
import android.widget.RelativeLayout.LayoutParams;

public class Setup extends FragmentActivity implements Camera.PreviewCallback{

    private ViewPager mPager;
    private PagerAdapter mPagerAdapter;

    CameraActivationFragment CAF;
    Camera cameraObj;
    FrameLayout preview;
    private CameraSurfacePreview mPreview;
    private int FRONT_CAMERA_INDEX = 1;

    private boolean qCommHardware;
    public static FacialProcessing facialProc;

    LayoutParams mParams;

    Parameters cParams;
    int cWidth;
    int cHeight;

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

        hideActionBar();

        mPager = (ViewPager) findViewById(R.id.pager);
        mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
        mPager.setAdapter(mPagerAdapter);

        checkForHardware();
    }

    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
        public ScreenSlidePagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            switch (position){
            case 0:
                CAF = new CameraActivationFragment();
                return CAF;
            case 1:
                return new ScreenSlidePageFragment();
            }

            return null;

        }

        @Override
        public int getCount() {
            return 2;
        }
    }

    private void hideActionBar(){
        getActionBar().hide();
    }

    @Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        // TODO Auto-generated method stub

    }

    private void checkForHardware(){
        qCommHardware = FacialProcessing.isFeatureSupported(FacialProcessing.
                FEATURE_LIST.FEATURE_FACIAL_RECOGNITION);
        if(qCommHardware){
            facialProc = (FacialProcessing) FacialProcessing.getInstance();
            facialProc.setRecognitionConfidence(85);
        }else{
            finish();
        }
    }

    public void startCamera(){
        try{
            cameraObj = Camera.open(FRONT_CAMERA_INDEX);
        }
        catch (Exception ex){
            finish();
            Log.d("Aegis", "failed to open front facing camera " + ex.getMessage());
        }

        setRotation();

        mPreview = new CameraSurfacePreview(Setup.this, cameraObj);
        preview = (FrameLayout) findViewById(R.id.camera_activation_preview);

        if(preview == null){
            Log.d("Aegis","preview is null");
            return;
        }

        cParams = cameraObj.getParameters();
        cWidth = cParams.getPictureSize().width;
        cHeight = cParams.getPictureSize().height;

        mParams = (LayoutParams) preview.getLayoutParams();
        mParams.width = (int) (getResources().getDisplayMetrics().widthPixels / 1.5);
        mParams.height = (int) (mParams.width * ((double) cWidth / cHeight));

        preview.addView(mPreview, mParams);
        cameraObj.setPreviewCallback((PreviewCallback) Setup.this);
    }

    @Override
    protected void onPause() {
        super.onPause();
        preview.removeView(mPreview);
    }

    @Override
    protected void onResume() {
        super.onResume();


        //startCamera();
    }

    private void setRotation(){
        Display display = ((WindowManager)getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();

        if(display.getRotation() == Surface.ROTATION_0)
        {                         
            cameraObj.setDisplayOrientation(90);
        }
        if(display.getRotation() == Surface.ROTATION_270)
        {
            cameraObj.setDisplayOrientation(180);
        }
    }

}

Here is the fragment itself:

package me.bionicsheep.aegis;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class CameraActivationFragment extends Fragment {


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.camera_activation_layout, container, false);
        return rootView;
    }

}

and lastly heres the xml for the fragment

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

    <FrameLayout
        android:id="@+id/camera_activation_preview"
        android:scaleType="fitXY"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true" >
    </FrameLayout>

</RelativeLayout>

Answer 1

Okay so I remedied this problem by adding the following to my fragments class

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    ((Setup) getActivity()).startCamera();
}

which starts the camera after the view has been properly created and inflated. This alone causes issues when you exit the app and reenter (resume) since the onResume doesn't have the startCamera command. To fix this I just included this block of code to my main class

@Override
protected void onResume() {
    super.onResume();
    if(preview != null){
        startCamera();
    }
}