Java &引用；Android_摄像头应用程序意外停止。请再试一次。”；如何解决这个问题？

我是android开发新手。这是一个摄像头应用程序，没有编译错误。但是当在模拟器上运行它时，它将无法工作。它给出“不幸的是预览已停止”。然后，我在一部有“android 2.3.6”操作系统的手机上测试了它，然后还给出了一个错误“应用程序预览（process com.example.Preview）意外停止。请重试。”

Preview.java

    package com.rrd.perview;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
//import android.R.color;
//import android.R.string;
import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.hardware.Camera;
import android.hardware.Camera.PreviewCallback;
import android.hardware.Camera.CameraInfo;
import android.os.Build;
//import android.os.Environment;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

class Preview extends SurfaceView implements SurfaceHolder.Callback{

    private static final String TAG = "Preview";
    SurfaceHolder mHolder;
    public Camera camera;

    //@SuppressWarnings("deprecation")
    Preview (Context context){
        super(context);

        mHolder = getHolder();
        mHolder.addCallback(this);
        //mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    @TargetApi(Build.VERSION_CODES.GINGERBREAD)
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        Camera.open(CameraInfo.CAMERA_FACING_BACK);
        try {
            camera.setPreviewDisplay(holder);

            camera.setPreviewCallback(new PreviewCallback() {


                public void onPreviewFrame(byte[] data, Camera camera) {
                    // TODO Auto-generated method stub
                    FileOutputStream outStream = null;

                    try{
                    outStream = new FileOutputStream(String.format("/sdcard/%d.jpg",System.currentTimeMillis()));
                    outStream.write(data);
                    outStream.close();
                    Log.d(TAG,"onPreviewFrame - wrote bytes: "+ data.length);

                    } catch(FileNotFoundException e){
                        e.printStackTrace();                        
                    } catch(IOException e){
                        e.printStackTrace();
                    }finally{

                    }
                    Preview.this.invalidate();                  

                }
            });
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub

        camera.stopPreview();
        camera = null;      
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // TODO Auto-generated method stub
        Camera.Parameters parameters = camera.getParameters();
        parameters.setPreviewSize(w, h);
        camera.setParameters(parameters);
        camera.startPreview();

    }

    public void drow(Canvas canvas){
        super.draw(canvas);
        Paint p = new Paint(Color.RED);
        Log.d(TAG, "drow");
        canvas.drawText("Preview",canvas.getWidth()/2,canvas.getHeight()/2, p);
    }




}


activity_main.xml

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <FrameLayout android:id="@+id/preview"
        android:layout_weight="1" 
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">
</FrameLayout>  

    <Button android:layout_width="wrap_content"
        android:layout_height="wrap_content" 
        android:id="@+id/buttonClick"
        android:text="Click" android:layout_gravity="center">        
    </Button>

</RelativeLayout>

---

你的问题是什么？到目前为止你试过什么？ 要记住几点：

• 当使用摄像头时，您需要在清单中声明“android.permission.camera”——在您的清单中还没有看到
• 您有java.lang.NullPointerException，请检查是哪一行引起的
• 在surfaceCreated（）中，您正在执行以下操作：
  摄像头。打开（CameraRinfo.摄像头面向后方）

然后你使用的是摄影机对象，它没有初始化！将上述内容更改为：

camera = Camera.open(CameraInfo.CAMERA_FACING_BACK);

并检查RuntimeException，如果打开摄影机失败，您可能会得到该异常

请查看有关摄像头控制的Android培训课程：

在您的代码中有一些东西是空的（Preview.java:43）。。。调试它

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

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />
    <uses-permission android:name="android.permission.CAMERA"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.rrd.perview.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>
    </application>

</manifest>

11-20 05:02:23.974: D/CameraDemo(1075): onCreate'd
11-20 05:02:24.804: D/AndroidRuntime(1075): Shutting down VM
11-20 05:02:24.804: W/dalvikvm(1075): threadid=1: thread exiting with uncaught exception (group=0xb1b0ab90)
11-20 05:02:24.884: E/AndroidRuntime(1075): FATAL EXCEPTION: main
11-20 05:02:24.884: E/AndroidRuntime(1075): Process: com.rrd.perview, PID: 1075
11-20 05:02:24.884: E/AndroidRuntime(1075): java.lang.NullPointerException
11-20 05:02:24.884: E/AndroidRuntime(1075):     at com.rrd.perview.Preview.surfaceCreated(Preview.java:43)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.SurfaceView.updateWindow(SurfaceView.java:572)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.SurfaceView.access$000(SurfaceView.java:86)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:175)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:847)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1869)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.Choreographer.doFrame(Choreographer.java:532)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.os.Handler.handleCallback(Handler.java:733)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.os.Handler.dispatchMessage(Handler.java:95)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.os.Looper.loop(Looper.java:137)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at android.app.ActivityThread.main(ActivityThread.java:4998)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at java.lang.reflect.Method.invokeNative(Native Method)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at java.lang.reflect.Method.invoke(Method.java:515)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-20 05:02:24.884: E/AndroidRuntime(1075):     at dalvik.system.NativeStart.main(Native Method)
11-20 05:03:03.864: I/Process(1075): Sending signal. PID: 1075 SIG: 9

camera = Camera.open(CameraInfo.CAMERA_FACING_BACK);