一般情况下调用系统相机就足够了，但比如扫描二维码则需要自定义拍照界面

我们写一个范例创建自定义拍照界面，我们会使用 SurfaceView 作为我们的预览界面

1. 创建一个 空的 Android 项目 cn.twle.android.CustomCamera

2. 修改 activity_main.xml 添加一个简单的 SurfaceView + Button

   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center_horizontal"
       android:orientation="vertical">
   
       <SurfaceView
           android:id="@+id/sfv_preview"
           android:layout_marginTop="100dp"
           android:layout_width="200dp"
           android:layout_height="200dp" />
   
       <Button
           android:id="@+id/btn_take"
           android:layout_marginTop="32dp"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="拍照" />
   
   </LinearLayout>
   

3. 创建 activity_preview.xml

   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <ImageView
           android:id="@+id/preview"
           android:layout_marginTop="100dp"
           android:layout_width="200dp"
           android:layout_height="200dp" />
   
   </LinearLayout>
   

4. 然后创建一个 PreviewActivity.java 用于预览内容

   package cn.twle.android.customcamera;
   
   import android.net.Uri;
   import android.os.Bundle;
   import android.support.v7.app.AppCompatActivity;
   import android.widget.ImageView;
   
   import java.io.File;
   
   public class PreviewActivity extends AppCompatActivity {
       @Override
       public void onCreate(Bundle savedInstanceState) {
   
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_preview);
   
           ImageView img = findViewById(R.id.preview);
           String path = getIntent().getStringExtra("path");
           if(path != null){
               img.setImageURI(Uri.fromFile(new File(path)));
           }
       }
   }
   

5. 修改 AndroidManifest.xml 添加调用系统相机权限和注册 PreviewActivity

   调用系统相机权限

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

   注册 PreviewActivity

   <activity android:name=".PreviewActivity" />
   

6. 修改 MainActivity.java 拍照并保存照片

   package cn.twle.android.customcamera;
   
   import android.content.Intent;
   import android.hardware.Camera;
   import android.support.v7.app.AppCompatActivity;
   import android.os.Bundle;
   import android.view.SurfaceHolder;
   import android.view.SurfaceView;
   import android.view.View;
   import android.widget.Button;
   import android.widget.Toast;
   
   import java.io.File;
   import java.io.FileOutputStream;
   import java.io.IOException;
   
   public class MainActivity extends AppCompatActivity {
   
       private SurfaceView sfv_preview;
       private Button btn_take;
       private Camera camera = null;
       private SurfaceHolder.Callback cpHolderCallback = new SurfaceHolder.Callback() {
           @Override
           public void surfaceCreated(SurfaceHolder holder) {
               startPreview();
           }
   
           @Override
           public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
   
           }
   
           @Override
           public void surfaceDestroyed(SurfaceHolder holder) {
               stopPreview();
           }
       };
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           bindViews();
       }
   
       private void bindViews() {
           sfv_preview = (SurfaceView) findViewById(R.id.sfv_preview);
           btn_take = (Button) findViewById(R.id.btn_take);
           sfv_preview.getHolder().addCallback(cpHolderCallback);
   
           btn_take.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View v) {
                   camera.takePicture(null, null, new Camera.PictureCallback() {
                       @Override
                       public void onPictureTaken(byte[] data, Camera camera) {
                           String path = "";
                           if ((path = saveFile(data)) != null) {
                               Intent it = new Intent(MainActivity.this, PreviewActivity.class);
                               it.putExtra("path", path);
                               startActivity(it);
                           } else {
                               Toast.makeText(MainActivity.this, "保存照片失败", Toast.LENGTH_SHORT).show();
                           }
                       }
                   });
               }
           });
       }
   
       //保存临时文件的方法
       private String saveFile(byte[] bytes){
           try {
               File file = File.createTempFile("img","");
               FileOutputStream fos = new FileOutputStream(file);
               fos.write(bytes);
               fos.flush();
               fos.close();
               return file.getAbsolutePath();
           } catch (IOException e) {
               e.printStackTrace();
           }
           return "";
       }
   
       //开始预览
       private void startPreview(){
           camera = Camera.open();
           try {
               camera.setPreviewDisplay(sfv_preview.getHolder());
               camera.setDisplayOrientation(90);   //让相机旋转90度
               camera.startPreview();
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
   
       //停止预览
       private void stopPreview() {
           camera.stopPreview();
           camera.release();
           camera = null;
       }
   
   }