Android4.4实现简单的录像功能

一、前言

在Android中实现录像功能，高版本Android和低版本Android的API使用方式不同。本文以Android4.4系统为基础，简单的列举一下实现过程。

二、步骤

要在 Android 4.4 中实现录像功能，可按照以下步骤进行操作：

1. 在布局文件中添加一个 SurfaceView 控件，作为预览画面的容器。

2. 获取 Camera 对象，并设置参数配置和预览界面。

3. 创建一个 MediaRecorder 对象，并设置相关参数，如编码方式、分辨率、帧率等。同时，还需要指定输出文件的路径和格式。

4. 在录像开始前，先调用 Camera 的 stopPreview() 方法停止预览，然后调用 MediaRecorder 的 prepare() 方法进行初始化。

5. 开始录像，调用 MediaRecorder 的 start() 方法开始录制视频。

6. 结束录像，调用 MediaRecorder 的 stop() 方法停止录制。然后记得要释放 MediaRecorder 对象。

7. 最后，再调用 Camera 的 startPreview() 方法重新开始预览。

三、代码实现

1. 布局等相关文件实现

   布局里面包含一个SurfaceView组件和Button组件，activity_main.xml文件如下：

   
   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:id="@+id/container"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
   
       <SurfaceView
           android:id="@+id/surface_view"
           android:layout_width="match_parent"
           android:layout_height="match_parent" />
   
       <Button
           android:id="@+id/btn_record"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:layout_alignParentBottom="true"
           android:layout_centerHorizontal="true"
           android:layout_marginBottom="16dp"
           android:text="@string/record_start"
           android:onClick="onClick"/>
   
   RelativeLayout>
   

   strings.xml文件，用于字符串操作，实现如下：

   <resources>
       <string name="app_name">Recordstring>
       <string name="record_start">录制string>
       <string name="record_stop">停止string>
   resources>
   

2. 具体代码实现

   新建一个MainActivity.java文件，实现如下：

   package com.example.record;
   
   import android.annotation.SuppressLint;
   import android.app.Activity;
   import android.hardware.Camera;
   import android.media.MediaRecorder;
   import android.os.Bundle;
   import android.os.Environment;
   import android.os.Handler;
   import android.os.Message;
   import android.util.Log;
   import android.view.SurfaceHolder;
   import android.view.SurfaceView;
   import android.view.View;
   import android.widget.Button;
   
   import java.io.File;
   import java.io.IOException;
   import java.text.SimpleDateFormat;
   import java.util.Date;
   
   public class MainActivity extends Activity implements SurfaceHolder.Callback {
   
       private static final String TAG = "MainActivity";
   
       // 默认为true
       private static boolean mIsRecording = false;
   
   
       private Button mRecordButton = null;
       private SurfaceView mSurfaceView = null;
       private SurfaceHolder mSurfaceHolder = null;
       private MediaRecorder mMediaRecorder = null;
   
       private Camera mCamera = null;
   
       private static final int MSG_UPDATE_BUTTON_TEXT = 0x00;
   
       @SuppressLint("HandlerLeak")
       private Handler mHandler = new Handler() {
           @Override
           public void handleMessage(Message msg) {
               super.handleMessage(msg);
   
               switch (msg.what) {
                   case MSG_UPDATE_BUTTON_TEXT:
                       if (mRecordButton != null) {
                           mRecordButton.setText(String.valueOf(msg.obj));
                       }
                       break;
                       default:
                           break;
               }
           }
       };
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           Log.d(TAG, "onCreate");
           setContentView(R.layout.activity_main);
   
           initView();
       }
   
       @Override
       protected void onResume() {
           super.onResume();
           Log.d(TAG, "onDestroy");
       }
   
       @Override
       protected void onDestroy() {
           super.onDestroy();
           Log.d(TAG, "onDestroy");
           if (mIsRecording) {
               stopRecording();
           }
       }
   
       // 初始化View 组件
       private void initView() {
           Log.d(TAG, "initView");
           if (mRecordButton == null) {
               mRecordButton = (Button) findViewById(R.id.btn_record);
           }
   
           if (mSurfaceView == null) {
               mSurfaceView = (SurfaceView) findViewById(R.id.surface_view);
   
               if (mSurfaceHolder == null) {
                   mSurfaceHolder = mSurfaceView.getHolder();
                   mSurfaceHolder.addCallback(this);
               }
           }
       }
   
       public void onClick(View view) {
           // 开始录制
           if (!mIsRecording) {
               mIsRecording = true;
               if (mHandler != null) {
                   Message msg = new Message();
                   msg.what = MSG_UPDATE_BUTTON_TEXT;
                   msg.obj = getText(R.string.record_stop);
                   mHandler.dispatchMessage(msg);
   
                   startRecording();
               }
           } else { // 停止录制
               mIsRecording = false;
               if (mHandler != null) {
                   Message msg = new Message();
                   msg.what = MSG_UPDATE_BUTTON_TEXT;
                   msg.obj = getText(R.string.record_start);
                   mHandler.dispatchMessage(msg);
   
                   stopRecording();
               }
           }
       }
   
       @Override
       public void surfaceCreated(SurfaceHolder holder) {
           Log.d(TAG, "surfaceCreated");
           mCamera = openCamera();
       }
   
       @Override
       public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
           Log.d(TAG, "surfaceChanged");
           if (mCamera != null && mSurfaceHolder != null) {
   
               try {
                   mCamera.stopPreview();
               } catch (Exception e) {
                   e.printStackTrace();
               }
   
               Camera.Parameters parameters = mCamera.getParameters();
               mCamera.setParameters(parameters);
               try {
                   mCamera.setPreviewDisplay(mSurfaceHolder);
                   mCamera.startPreview();
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
       }
   
       @Override
       public void surfaceDestroyed(SurfaceHolder holder) {
           Log.d(TAG, "surfaceDestroyed");
           releaseCamera();
       }
   
       // 打开相机
       private Camera openCamera() {
           Camera camera;
           try {
               camera = Camera.open(0);
           } catch (Exception e) {
               e.printStackTrace();
               Log.e(TAG, "open camera failed!!");
               return null;
           }
           Log.d(TAG, "open camera success!!");
           return camera;
       }
   
       // 销毁相机
       private void releaseCamera() {
           if (mCamera != null) {
               mCamera.stopPreview();
               mCamera.release();
               mCamera = null;
           }
       }
   
       private void startRecording() {
           if (mCamera == null) {
               Log.e(TAG, "startRecording, mCamera is null");
               return;
           }
   
           mMediaRecorder = new MediaRecorder();
           mCamera.unlock();
           mMediaRecorder.setCamera(mCamera);
           mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
           mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
           mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
           mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
           mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
           mMediaRecorder.setVideoEncodingBitRate(3 * 1024 * 1024);
           mMediaRecorder.setVideoFrameRate(30);
           mMediaRecorder.setVideoSize(1280, 960);
           String saveName = getOutputMediaFileName();
           if (saveName == null) {
               Log.e(TAG, "save media file error: " + saveName);
               return;
           }
           mMediaRecorder.setOutputFile(saveName);
   
           try {
               mMediaRecorder.prepare();
               mMediaRecorder.start();
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
   
       private void stopRecording() {
           if (mMediaRecorder != null) {
               try {
                   mMediaRecorder.stop();
                   mMediaRecorder.release();
               } catch (Exception e) {
                   e.printStackTrace();
               }
               mMediaRecorder = null;
   
               mCamera.lock();
           }
   
           mIsRecording = false;
       }
   
       private String getOutputMediaFileName() {
           String state = Environment.getExternalStorageState();
           // Check if external storage is mounted
           if (!Environment.MEDIA_MOUNTED.equals(state)) {
               Log.e(TAG, "External storage is not mounted!");
               return null;
           }
   
           File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
                   Environment.DIRECTORY_DCIM), "");
           // Create the storage directory if it does not exist
           if (!mediaStorageDir.exists()) {
               if (!mediaStorageDir.mkdirs()) {
                   Log.e(TAG, "Failed to create directory " + mediaStorageDir.getPath()
                           + " for pictures/video!");
                   return null;
               }
           }
   
           // Create a media file name
           @SuppressLint("SimpleDateFormat") String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
           String mediaFileName = mediaStorageDir.getPath() + File.separator +
                   "VID_" + timeStamp + ".mp4";
   
           return mediaFileName;
       }
   }
   

3. AndroidManifest.xml文件

   
   <manifest xmlns:android="http://schemas.android.com/apk/res/android"
       package="com.example.record">
   
       <uses-permission android:name="android.permission.CAMERA" />
       <uses-permission android:name="android.permission.RECORD_AUDIO" />
       <uses-feature android:name="android.hardware.camera" />
       <uses-feature android:name="android.hardware.camera.autofocus" />
   
       
       <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
       <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
   
       <application
           android:allowBackup="true"
           android:icon="@mipmap/ic_launcher"
           android:label="@string/app_name"
           android:supportsRtl="true"
           android:theme="@style/AppTheme">
   
           <activity android:name=".MainActivity">
               <intent-filter>
                   <action android:name="android.intent.action.MAIN" />
                   <category android:name="android.intent.category.DEFAULT" />
                   <category android:name="android.intent.category.LAUNCHER" />
               intent-filter>
           activity>
       application>
   
   manifest>
   

4. Android.mk文件

   有时候需要将apk放置AOSP源码中编译，Android.mk文件如下：

   LOCAL_PATH:= $(call my-dir)
   include $(CLEAR_VARS)
   
   LOCAL_SRC_FILES := $(call all-java-files-under, java)
   
   LOCAL_RESOURCE_DIR := $(LOCAL_PATH)/res
   
   LOCAL_MANIFEST_FILE :=  AndroidManifest.xml
   
   
   LOCAL_PACKAGE_NAME := Record
   ALL_DEFAULT_INSTALLED_MODULES += $(LOCAL_PACKAGE_NAME)
   
   #LOCAL_SDK_VERSION := current
   
   LOCAL_CERTIFICATE := platform
   
   #LOCAL_PRIVILEGED_MODULE := true
   
   include $(BUILD_PACKAGE)
   

四、注意事项

1. 在使用 Camera 时，必须在 AndroidManifest.xml 文件中添加 CAMERA、存储等相关 权限。

2. 在录像结束后，需要及时释放资源，避免占用过多的系统资源。

3. 由于不同设备品牌的摄像头硬件和软件实现有所差异，因此在不同设备上的录像效果可能会有所不同。