java - 您如何获得适用于 Android 的简单相机程序？

Question

我刚开始用 Java 编程，我需要建立一个简单的应用程序来显示相机、拍照并将照片数据发送到某处。

我一直在网上搜索，试图找到一个按预期工作的好相机教程，但显然它们都需要一些我还没有的内在知识。

关于 this页面上，commonsWare 指向其中包含一些用于使用相机的示例代码的代码。我已经获取了 PictureDemo 代码并使其正常运行。但是，它只会显示黑屏。我认为这是因为程序实际上并没有在主要功能中激活预览或相机，但每次我尝试添加我认为我需要的代码时，我都会遇到异常。

所以我的问题是，我需要在 main 函数中添加什么才能让相机运行？或者是否有更好的教程可以让我看到启动相机的简单基本代码？

package assist.core;

import android.app.Activity;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.KeyEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;
import java.io.File;
import java.io.FileOutputStream;

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

public class MainActivity extends Activity
{
    private SurfaceView preview = null;
    private SurfaceHolder previewHolder = null;
    private Camera camera = null;
    private boolean inPreview = false;

    /**
     * 
     */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        //Call the parent class
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        preview = (SurfaceView) findViewById(R.id.preview);
        previewHolder = preview.getHolder();
        previewHolder.addCallback(surfaceCallback);
        previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    @Override
    public void onResume() {
        super.onResume();
        //Get the camera instance
        camera = CameraFinder.INSTANCE.open();
    }

    @Override
    public void onPause() {
        if (inPreview) {
            camera.stopPreview();
        }

        camera.release();
        camera = null;
        inPreview = false;

        super.onPause();
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_CAMERA || keyCode == KeyEvent.KEYCODE_SEARCH) {
            if (inPreview) {
                camera.takePicture(null, null, photoCallback);
                inPreview = false;
            }

            return(true);
        }

        return(super.onKeyDown(keyCode, event));
    }

    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);
    }

    SurfaceHolder.Callback surfaceCallback = new SurfaceHolder.Callback() {
        public void surfaceCreated(SurfaceHolder holder) {
            try {
                camera.setPreviewDisplay(previewHolder);
            }
            catch (Throwable t) {
                Log.e("MainActivity-surfaceCallback", "Exception in setPreviewDisplay()", t);
                Toast.makeText(MainActivity.this, t.getMessage(), Toast.LENGTH_LONG).show();
            }
        }

        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            Camera.Parameters parameters = camera.getParameters();
            Camera.Size size = getBestPreviewSize(width, height, parameters);

            if (size != null) {
                parameters.setPreviewSize(size.width, size.height);
                parameters.setPictureFormat(PixelFormat.JPEG);

                camera.setParameters(parameters);
                camera.startPreview();
                inPreview = true;
            }
        }

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

    Camera.PictureCallback photoCallback = new Camera.PictureCallback() {
        public void onPictureTaken(byte[] data, Camera camera) {
            new SavePhotoTask().execute(data);
            camera.startPreview();
            inPreview = true;
        }
    };

    class SavePhotoTask extends AsyncTask<byte[], String, String> {
        @Override
        protected String doInBackground(byte[]... jpeg) {
            File photo = new File(Environment.getExternalStorageDirectory(), "photo.jpg");
            if(photo.exists()) {
                photo.delete();
            }

            try {
                FileOutputStream fos = new FileOutputStream(photo.getPath());
                fos.write(jpeg[0]);
                fos.close();
            }
            catch (java.io.IOException e) {
                Log.e("MainActivity", "Exception in photoCallback", e);
            }

            return(null);
        }
    }
}

更新

至于我得到的异常，如果我尝试像下面的代码那样制作主函数，

public void onCreate(Bundle savedInstanceState)
{
    //Call the parent class
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    preview = (SurfaceView) findViewById(R.id.preview);
    previewHolder = preview.getHolder();
    previewHolder.addCallback(surfaceCallback);
    previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

    Camera.Parameters parameters = camera.getParameters();
    parameters.setPictureFormat(PixelFormat.JPEG);
    camera.setParameters(parameters);

    try {
        //Start the camera preview display
        camera.setPreviewDisplay(previewHolder);
        camera.startPreview();
    } 
    catch (IOException ex) {
        Logger.getLogger(MainActivity.class.getName()).log(Level.SEVERE, null, ex);
    }
}

我收到“应用程序意外停止。请重试。”我基本上是在尝试按照 android documention 的步骤进行操作指定。我也试过在获取相机对象后将这段代码放入 onResume 函数中，然后调用 this.onResume。

Answer 1

这是一个使用 Intents 的全功能相机(我立即调用相机，你显然会包含一个按钮或菜单项)。它将图像保存到图库并作为 Pic.jpg 根目录，然后显示捕获的图像。

此答案是 this EXCELLENT snippet by Aleksander O. 的扩展和完整版本

import java.io.File;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;

public class CallCameraActivity extends Activity {

    final int TAKE_PICTURE = 1;
    private Uri imageUri;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        takePhoto();
    }



    public void takePhoto() {
        Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
        File photo = new File(Environment.getExternalStorageDirectory(),  "Pic.jpg");
        intent.putExtra(MediaStore.EXTRA_OUTPUT,
                Uri.fromFile(photo));
        imageUri = Uri.fromFile(photo);
        startActivityForResult(intent, TAKE_PICTURE);
    }
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {

    super.onActivityResult(requestCode, resultCode, data);
    switch (requestCode) {
    case TAKE_PICTURE:
        if (resultCode == Activity.RESULT_OK) {
            //Uri imageUri;
            Uri selectedImage = imageUri;
            getContentResolver().notifyChange(selectedImage, null);
            ImageView imageView = (ImageView) findViewById(R.id.IMAGE);
            ContentResolver cr = getContentResolver();
            Bitmap bitmap;
            try {
                 bitmap = android.provider.MediaStore.Images.Media
                 .getBitmap(cr, selectedImage);

                imageView.setImageBitmap(bitmap);
                Toast.makeText(this, "This file: "+selectedImage.toString(),
                        Toast.LENGTH_LONG).show();
            } catch (Exception e) {
                Toast.makeText(this, "Failed to load", Toast.LENGTH_SHORT)
                        .show();
                Log.e("Camera", e.toString());
            }
        }
    }
}
}

将其用作您的 main.xml 布局

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

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />


    <ImageView
        android:id="@+id/IMAGE"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher" />

</LinearLayout>

字符串.xml

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<resources>
  <string name="hello">Hello World, TonyPicturesInc!</string>
  <string name="app_name">TGCam</string>
</resources>