Android 相机预览为空白

我已经研究了几天了，我最后的办法就是问比我知道得更多的人。我一直在学习教程和代码。我无法执行创建相机预览的简单功能。我对保存快照不感兴趣，只是在应用程序中查看车载摄像头。任何帮助都将不胜感激。我的最终目标是预览一台IP摄像机。是否有一个完整的代码，我可以玩这个应用程序，或者有人可以让我知道为什么这个代码不工作

主要内容如下： 包com.example.cameracontrol

    import android.os.Bundle;
    import android.app.Activity;
    import android.view.Menu;

    public class MainActivity extends Activity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.main, menu);
            return true;
        }
    }

CameraPreview类：

    import java.io.IOException;
    import java.util.List;
    import android.annotation.SuppressLint;
    import android.app.Activity;
    import android.content.Context;
    import android.hardware.Camera;
    import android.hardware.Camera.Size;
    import android.util.Log;
    import android.view.Surface;
    import android.view.SurfaceHolder;
    import android.view.SurfaceView;

    @SuppressLint("ViewConstructor")
    public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

        private static final String TAG = "CameraPreview";
        private SurfaceHolder mHolder;
        private Camera mCamera;
        private Size mPreviewSize; 

        @SuppressWarnings("deprecation")
        public CameraPreview(Context context, Camera camera, Activity activity) {
            super(context);
            mCamera = camera;
            // 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);
        }

                public void surfaceCreated(SurfaceHolder holder) {
            // The Surface has been created, now tell the camera where to draw the preview.
                    try {
                mCamera.setPreviewDisplay(holder);
                mCamera.startPreview();
            } 
            catch (IOException e) {
                Log.d(TAG, "Error setting camera preview: " + e.getMessage());
            }
        }

        public void surfaceDestroyed(SurfaceHolder holder) {
            // empty. Take care of releasing the Camera preview in your activity.
        }

        public void surfaceChanged(SurfaceHolder holder, int format, int w, int h)         {
            // If your preview can change or rotate, take care of those events here.
            // Make sure to stop the preview before resizing or reformatting it.
            if (mHolder.getSurface() == null){
                // preview surface does not exist
                return;
            }

            // stop preview before making changes
            try{
                mCamera.stopPreview();
                } 
            catch (Exception e){
                // ignore: tried to stop a non-existent preview
                }

            // set preview size and make any resize, rotate or
            // reformatting changes here
            /**Camera.Parameters parameters = mCamera.getParameters();
            List<Size> localSizes = mCamera.getParameters().getSupportedPreviewSizes();
            mPreviewSize = localSizes.get(0);
            Log.d(TAG, "Width " + mPreviewSize.width);
            Log.d(TAG, "Height " + mPreviewSize.height);

            parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height );
            requestLayout();
            mCamera.setParameters(parameters);*/

            Camera.Parameters p = mCamera.getParameters();
            p.setPreviewSize(w, h);
            mCamera.setParameters(p);

            //start preview with new settings
            try {
                mCamera.setPreviewDisplay(mHolder);
                mCamera.startPreview();
            } 
    catch (Exception e){
                Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }
        }

        @SuppressLint("NewApi")
        public static void setCameraDisplayOrientation(Activity activity, int cameraId, android.hardware.Camera camera) {
             android.hardware.Camera.CameraInfo info = new         android.hardware.Camera.CameraInfo();
             android.hardware.Camera.getCameraInfo(cameraId, info);
             int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
             int degrees = 0;
             int result;

             switch (rotation) {
                 case Surface.ROTATION_0: degrees = 0; break;
                 case Surface.ROTATION_90: degrees = -90; break;
                 case Surface.ROTATION_180: degrees = 0; break;
                 case Surface.ROTATION_270: degrees = -90; break;
             }

             if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
                 result = (info.orientation + degrees) % 360;
                 result = (360 - result) % 360;  // compensate the mirror
             } 
             else {  // back-facing
                 result = (info.orientation - degrees + 360) % 360;
             }
             camera.setDisplayOrientation(result);
        }
    }

活动_main.xml：

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:baselineAligned="false"
        android:layout_width="match_parent"
        android:layout_height="match_parent"

        tools:context=".CameraActivity" >


        <FrameLayout
        android:id="@+id/camera_preview"
        android:layout_width="0dip"
        android:layout_height="wrap_content"
        android:layout_weight = "1" />

    </LinearLayout>

舱单：

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.cameracontrol"
        android:versionCode="1"
        android:versionName="1.0" >

        <uses-sdk
            android:minSdkVersion="8"
            android:targetSdkVersion="19" />

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

        <application
            android:allowBackup="true"
            android:icon="@drawable/ic_launcher"
            android:label="@string/app_name"
            android:theme="@style/AppTheme" >

            <activity
                android:name="com.example.cameracontrol.MainActivity"
                android:label="@string/app_name" >
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>

            <activity android:name=".CameraActivity"
                android:label="@string/app_name"

                android:screenOrientation="landscape">
                <!-- configure this activity to use landscape orientation -->
            </activity>

        </application>

    </manifest>

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.cameracontrol"
        android:versionCode="1"
        android:versionName="1.0" >

        <uses-sdk
            android:minSdkVersion="8"
            android:targetSdkVersion="19" />

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

        <application
            android:allowBackup="true"
            android:icon="@drawable/ic_launcher"
            android:label="@string/app_name"
            android:theme="@style/AppTheme" >

            <activity
                android:name="com.example.cameracontrol.MainActivity"
                android:label="@string/app_name" >
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>

            <activity android:name=".CameraActivity"
                android:label="@string/app_name"

                android:screenOrientation="landscape">
                <!-- configure this activity to use landscape orientation -->
            </activity>

        </application>

    </manifest>