Question

我正在尝试创建一个包含3个片段的应用程序，我正在使用viewpager扫描它们。
第一个是列表，第二个应该是摄像头，第三个是列表滑动工作，但当我到达第二个片段时，cameraPreview是黑色的。

我没有崩溃或其他不同的堆栈跟踪我之前已经创建了这个应用程序的一部分，但没有刷过它确实有效。我在新应用程序中再次设置时没有更改片段，我只是将android.app.Fragment的导入更改为android.support.v4.app.Fragment。

我用这个例子来创建应用程序：
ViewPager with multiple Fragments and Layout files - How To
我的情况并没有那么不同，我想感谢Haxor提供了很好的解释，这对我很有帮助。我无法支持它，所以我会用这种方式感谢你:)）

MainActivity.class：

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.Menu;
import android.view.MenuItem;
import android.view.SurfaceView;
import android.view.View;
import android.widget.LinearLayout;


public class MainActivity extends FragmentActivity {

LinearLayout ButtonBar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ViewPager pager = (ViewPager) findViewById(R.id.viewPager);
    pager.setAdapter(new MyPagerAdapter(getSupportFragmentManager()));
}


private class MyPagerAdapter extends FragmentPagerAdapter {

    public MyPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int pos) {
        switch(pos) {
            case 0:
                return FirstFragment.newInstance("FirstFragment, Instance 1");
            case 1:
                return SecondFragment.newInstance("SecondFragment, Instance 1");
            case 2:
                return ThirdFragment.newInstance("ThirdFragment, Instance 1");
            default:
                return ThirdFragment.newInstance("ThirdFragment, Default");
        }
    }

    @Override
    public int getCount() {
        return 3;
    }
}
}

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:context=".MainActivity"
android:background="#ffff">

<android.support.v4.view.ViewPager
    android:id="@+id/viewPager"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"/>
</RelativeLayout>

第二个fragment.class：

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.hardware.Camera;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.io.IOException;
import java.io.OutputStream;

/**
 * Created by Gebruiker on 29-10-2014.
 */
public class SecondFragment extends Fragment {

View rootView;
ImageButton cameraShootButton;
ImageButton cameraChangeButton;
Boolean switching = false;
View.OnClickListener tapper = null;
SurfaceView cameraPreview = null;
SurfaceHolder cameraPreviewHolder = null;
Camera camera = null;
boolean inPreview = false;
boolean cameraConfigured = false;
Integer currentCamera;

public static SecondFragment newInstance(String text) {

    SecondFragment f = new SecondFragment();
    Bundle b = new Bundle();
    b.putString("msg", text);

    f.setArguments(b);

    return f;
}

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


    cameraShootButton = (ImageButton) rootView.findViewById(R.id.captureB);
    cameraChangeButton = (ImageButton) rootView.findViewById(R.id.changeCameraB);
    cameraPreview = (SurfaceView) rootView.findViewById(R.id.cameraView);

    cameraPreviewHolder = cameraPreview.getHolder();
    cameraPreviewHolder.addCallback(surfaceCallback);
    cameraPreviewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);


    tapper = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (v.getId() == R.id.captureB) {
                camera.takePicture(ShutterCallback, PictureCallbackRaw, null, PictureCallbackJpeg);
            } else if (v.getId() == R.id.changeCameraB) {
                if (switching == true){
                    return;
                }
                changeCamera();
            }
        }
    };

    cameraShootButton.setOnClickListener(tapper);
    cameraChangeButton.setOnClickListener(tapper);
    return rootView;
}

@Override
public void onResume() {
    super.onResume();
    camera = getCamera("back");
    currentCamera = 1;
    startPreview();
}

@Override
public void onPause() {
    if (inPreview) {
        camera.stopPreview();
    }
    camera.release();
    camera = null;
    inPreview = false;

    super.onPause();
}

private Camera.Size getBestPreviewSize(int width, int height,
                                       Camera.Parameters parameters) {
    Camera.Size result = null;

    for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
        if (size.width <= width && size.height <= height) {
            if (result == null) {
                result = size;
            } else {
                int resultArea = result.width * result.height;
                int newArea = size.width * size.height;

                if (newArea > resultArea) {
                    result = size;
                }
            }
        }
    }

    return (result);
}

private void initPreview(int width, int height) {
    if (camera != null && cameraPreviewHolder.getSurface() != null) {
        try {
            camera.setPreviewDisplay(cameraPreviewHolder);
        } catch (Throwable t) {
            Log.e("PreviewDemo-surfaceCallback",
                    "Exception in setPreviewDisplay()", t);
        }

        if (!cameraConfigured) {
            Camera.Parameters parameters = camera.getParameters();
            Log.v("CAMERA", parameters.toString());
            Camera.Size size = getBestPreviewSize(width, height,
                    parameters);

            if (size != null) {
                Log.v("CameraPreviewHeight", ""+cameraPreview.getMeasuredHeight());
                Log.v("CameraRES", size.width + " " + size.height);
                parameters.setPreviewSize(size.width, size.height);
                camera.setParameters(parameters);
                cameraConfigured = true;
            }
        }
    }
}

private void startPreview() {
    if (cameraConfigured && camera != null) {
        camera.startPreview();
        inPreview = true;
        camera.setDisplayOrientation(90);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) {
            camera.enableShutterSound(false);
        }
    }
}

private void changeCamera() {
    switching = true;
    if (inPreview) {
        camera.stopPreview();
        camera.setPreviewCallback(null);
    }
    camera.release();
    camera = null;
    inPreview = false;
    if (currentCamera==1){
        camera = getCamera("front");
        currentCamera =2;
    }
    else{
        camera = getCamera("back");
        currentCamera = 1;
    }
    camera.setDisplayOrientation(90);
    try {
        camera.setPreviewDisplay(cameraPreviewHolder);
        cameraPreviewHolder.addCallback(surfaceCallback);
        camera.startPreview();
    } catch (IOException e) {
        e.printStackTrace();
    }

    inPreview = true;

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) {
        camera.enableShutterSound(false);
    }
    switching = false;

}

SurfaceHolder.Callback surfaceCallback = new SurfaceHolder.Callback() {
    public void surfaceCreated(SurfaceHolder holder) {
        // no-op -- wait until surfaceChanged()
    }

    public void surfaceChanged(SurfaceHolder holder,
                               int format, int width,
                               int height) {
        initPreview(width, height);
        startPreview();
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // no-op
    }
};

Camera.ShutterCallback ShutterCallback = new Camera.ShutterCallback() {
    public void surfaceCreated(SurfaceHolder holder) {
        // no-op -- wait until surfaceChanged()
    }

    public void surfaceChanged(SurfaceHolder holder,
                               int format, int width,
                               int height) {
        initPreview(width, height);
        startPreview();
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // no-op
    }

    @Override
    public void onShutter() {

    }
};

Camera.PictureCallback PictureCallbackRaw = new Camera.PictureCallback() {
    public void surfaceCreated(SurfaceHolder holder) {
        // no-op -- wait until surfaceChanged()
    }

    public void surfaceChanged(SurfaceHolder holder,
                               int format, int width,
                               int height) {
        initPreview(width, height);
        startPreview();
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // no-op
    }

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

    }
};

Camera.PictureCallback PictureCallbackJpeg = new Camera.PictureCallback() {
    public void surfaceCreated(SurfaceHolder holder) {
        // no-op -- wait until surfaceChanged()
    }

    public void surfaceChanged(SurfaceHolder holder,
                               int format, int width,
                               int height) {
        initPreview(width, height);
        startPreview();
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // no-op
    }

    @Override
    public void onPictureTaken(byte[] byteData, Camera camera) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inSampleSize = 5;
        OutputStream bos = null;
        Bitmap m = BitmapFactory.decodeByteArray(byteData, 0, byteData.length, options);

        //m.compress(Bitmap.CompressFormat.PNG, 75, bos);
        //Log.v("CAPTURED", ""+bos);
    }
};

private Camera getCamera(String getCamera) {
    int cameraCount = 0;
    Camera cam = null;
    Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
    cameraCount = Camera.getNumberOfCameras();
    for (int camIdx = 0; camIdx < cameraCount; camIdx++) {
        Camera.getCameraInfo(camIdx, cameraInfo);
        if ((cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) && (getCamera == "front")) {
            try {
                cam = Camera.open(camIdx);
            } catch (RuntimeException e) {
                Log.e("TEST", "Camera failed to open: " + e.getLocalizedMessage());
            }
        }
        else if ((cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_BACK) && (getCamera == "back")) {
            try {
                cam = Camera.open(camIdx);
            } catch (RuntimeException e) {
                Log.e("TEST", "Camera failed to open: " + e.getLocalizedMessage());
            }
        }
    }
    return cam;
}


}

second_frag.xml

<?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.view.SurfaceView
    android:id="@+id/cameraView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_alignParentBottom="true">

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:gravity="center">

        <ImageButton
            android:id="@+id/flitserB"
            android:layout_width="30dp"
            android:layout_height="70dp"
            android:scaleType="fitCenter"
            android:src="@drawable/flash"
            android:background="@null"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:gravity="center">
        <ImageButton
            android:id="@+id/captureB"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:scaleType="fitCenter"
            android:src="@drawable/camerashoot"
            android:background="@null"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:gravity="center">
        <ImageButton
            android:id="@+id/changeCameraB"
            android:layout_width="30dp"
            android:layout_height="70dp"
            android:scaleType="fitCenter"
            android:src="@drawable/camerachange"
            android:background="@null"/>

    </LinearLayout>

</LinearLayout>


</RelativeLayout>

Answer 1

可能您忘了向AndroidManifest.xml添加Camera权限：

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

见： http://developer.android.com/reference/android/hardware/Camera.html

Android ViewPager，片段中的cameraview没有显示

1 个答案: