Question

我正在学习Android Camera Api，我正在Nexus 6设备上进行测试。我下载了一个在设备上正常运行的Camera Api教程。然后我创建了自己的项目并基本上复制了代码，但每当我调用Camera.open（）时，它总是返回null。代码几乎完全相同。

清单也是相同的，我的gradle文件也是如此。

但我从网站上下载的教程是有效的，而我从Android Studio创建的教程却没有。

我无法弄清楚我做错了什么。我已经检查了以前关于这个问题的问题，我没有犯同样的错误。 Manifest权限位于正确的位置（应用程序标签上方），Nexus 6有后置摄像头，因此没有摄像头不是问题。

非工作清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.gr3ymatter.cameraapidemo">
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-feature android:name="android.hardware.camera" />
    <uses-feature android:name="android.hardware.camera.autofocus" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".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>

非工作主要活动：

import android.content.pm.ActivityInfo;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.hardware.Camera;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

    private ImageSurfaceView mImageSurfaceView;
    private Camera camera;

    private FrameLayout cameraPreviewLayout;
    private ImageView capturedImageHolder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

        cameraPreviewLayout = (FrameLayout)findViewById(R.id.camera_preview);
        capturedImageHolder = (ImageView)findViewById(R.id.captured_image);

        camera = checkDeviceCamera();
        mImageSurfaceView = new ImageSurfaceView(MainActivity.this, camera);
        cameraPreviewLayout.addView(mImageSurfaceView);

        Button captureButton = (Button)findViewById(R.id.button);
        captureButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                camera.takePicture(null, null, pictureCallback);
            }
        });
    }
    private Camera checkDeviceCamera(){
        Camera mCamera = null;
        try {
            mCamera = Camera.open();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return mCamera;
    }

    Camera.PictureCallback pictureCallback = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
            if(bitmap==null){
                Toast.makeText(MainActivity.this, "Captured image is empty", Toast.LENGTH_LONG).show();
                return;
            }
            capturedImageHolder.setImageBitmap(scaleDownBitmapImage(bitmap, 300, 200 ));
        }
    };

    private Bitmap scaleDownBitmapImage(Bitmap bitmap, int newWidth, int newHeight){
        Bitmap resizedBitmap = Bitmap.createScaledBitmap(bitmap, newWidth, newHeight, true);
        return resizedBitmap;
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

非工作SurfaceView类

import android.content.Context;
import android.hardware.Camera;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

import java.io.IOException;

/**
 * Created by Afzal on 2/2/16.
 */

public class ImageSurfaceView extends SurfaceView implements SurfaceHolder.Callback {

    private Camera camera;
    private SurfaceHolder surfaceHolder;

    public ImageSurfaceView(Context context, Camera camera) {
        super(context);
        this.camera = camera;
        this.surfaceHolder = getHolder();
        this.surfaceHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            this.camera.setPreviewDisplay(holder);
            this.camera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        this.camera.stopPreview();
        this.camera.release();
    }
}

工作项目文件与我按照示例复制它们时的文件相同。我可以将github链接粘贴到工作和非工作项目，如果这会有帮助吗？

编辑：这是两个项目的回购 https://github.com/Gr3ymatter/CameraApiDemo_Working https://github.com/Gr3ymatter/CameraApiDemo_NotWorking

编辑：LOGCAT输出。也基于Madhurs有用的评论，我想也许这是一个设备问题，所以我在Nexus 7上运行这个，但我仍然遇到了同样的问题。

提前感谢您的帮助！

Answer 1

由于Android 6.0，您需要在nexus 6中询问权限查看有关permissions

的更多信息

或者您可以将清单更改为

//make target lower then 23 then it will run properly in android M
    <uses-sdk
            android:minSdkVersion="15"
            android:targetSdkVersion="22" />

没有权限的示例

检查此示例希望它有所帮助，

https://github.com/pikanji/CameraPreviewSample

你的代码正在为我工作

Android：Camera.Open（）通过一个Project但不返回另一个Project返回null。相同的设备

1 个答案: