本文目的
使用 Camera API 進行視頻的採集,分別使用 SurfaceView、TextureView 來預覽 Camera 數據,取到 NV21 的數據回調
SurfaceView優缺點
優點:
可以在一個獨立的線程中進行繪製,不會影響主線程
使用雙緩衝機制,播放視頻時畫面更流暢
缺點:
Surface不在View hierachy中,它的顯示也不受View的屬性控制,所以不能進行平移,縮放等變換,也不能放在其它ViewGroup中。SurfaceView
不能嵌套使用。
TextureView作用
TextureView可用於顯示內容流,內容流可以是視頻或者OpenGL的場景。內容流可來自應用進程或是遠程其它進程。
Textureview必須在硬件加速開啓的窗口中使用。
注意:若是軟解,TextureView不會顯示東西。
TextureView優點及缺點
優點:
支持移動、旋轉、縮放等動畫,支持截圖
缺點:
必須在硬件加速的窗口中使用,佔用內存比SurfaceView高,在5.0以前在主線程渲染,5.0以後有單獨的渲染線程。
準備工作
添加相機權限
<uses-permission android:name="android.permission.CAMERA" />
注意:camera預覽回調中默認使用NV21格式
UI 準備
<!-- 全屏顯示 -->
<style name="FullScreenTheme" parent="AppTheme">
<item name="windowNoTitle">true</item>
<item name="android:windowFullscreen">true</item>
</style>
承載預覽圖像
<FrameLayout
android:id="@+id/camera_preview"
android:layout_width="match_parent"
android:layout_height="match_parent" />
使用 SurfaceView 預覽 Camera,取到NV21數據
- 自定義CameraPreview繼承SurfaceView,實現SurfaceHolder.Callback接口
- 獲取NV21數據,Camera.setPreviewCallback() 要放在Camera.startPreview() 之前。使用Camera.PreviewCallback獲取預覽數據回調。默認是NV21格式。
- surfaceChanged中,camera啓動預覽前可以進行設置,例如設置尺寸,調整方向
/**
* camera預覽視圖
* Created by on 2020/2/26.
*/
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private static final String TAG = "CameraPreview";
private SurfaceHolder mHolder;
private Camera mCamera;
private int mFrameCount = 0;
public CameraPreview(Context context) {
super(context);
}
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;
mHolder = getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera c) {
this.mCamera = c;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// 開啓預覽
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.d(TAG, "設置相機預覽失敗: " + e.getMessage());
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// 可在此釋放camera
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// 若需要旋轉、更改大小或重新設置,請確保證已停止預覽
if (mHolder.getSurface() == null) {
return;
}
try {
mCamera.stopPreview();
} catch (Exception e) {
// 在此停止不存在的預覽
}
Camera.Parameters parameters = mCamera.getParameters();
// ImageFormat.NV21 == 17
if (this.getResources().getConfiguration().orientation != Configuration.ORIENTATION_LANDSCAPE) {
mCamera.setDisplayOrientation(90);
} else {
mCamera.setDisplayOrientation(0);
}
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.setPreviewCallback(mCameraPreviewCallback); // 回調要放在 startPreview() 之前
mCamera.startPreview();
} catch (Exception e) {
Log.d(TAG, "開啓相機預覽失敗: " + e.getMessage());
}
}
private Camera.PreviewCallback mCameraPreviewCallback = new Camera.PreviewCallback() {
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
mFrameCount++;
Log.d(TAG, "onPreviewFrame: data.length=" + data.length + ", frameCount=" + mFrameCount);
}
};
}
爲了防止阻塞UI線程,在子線程中打開camera。camera常放在try catch中使用。
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private Camera mCamera;
private CameraPreview mPreview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new InitCameraThread().start();
}
@Override
protected void onResume() {
if (null == mCamera) {
if (safeCameraOpen()) {
mPreview.setCamera(mCamera); // 重新獲取camera操作權
} else {
Log.e(TAG, "無法操作camera");
}
}
super.onResume();
}
@Override
protected void onPause() {
super.onPause();
releaseCamera();
}
private boolean safeCameraOpen() {
boolean qOpened = false;
try {
releaseCamera();
mCamera = Camera.open();
qOpened = (mCamera != null);
} catch (Exception e) {
Log.e(TAG, "打開相機失敗");
e.printStackTrace();
}
return qOpened;
}
private void releaseCamera() {
if (mCamera != null) {
mCamera.setPreviewCallback(null);
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}
private class InitCameraThread extends Thread {
@Override
public void run() {
super.run();
if (safeCameraOpen()) {
Log.d(TAG, "開啓攝像頭");
runOnUiThread(new Runnable() {
@Override
public void run() {
mPreview = new CameraPreview(MainActivity.this, mCamera);
FrameLayout preview = findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
});
}
}
}
}
使用 TextureView 預覽 Camera,取到NV21數據
-
使用TextureView很簡單:獲取到它的SurfaceTexture,使用SurfaceTexture呈現內容。
-
CameraPreview繼承了TextureView,外部需要傳入camera實例。在onSurfaceTextureAvailable中,配置camera,比如設置圖像方向。
-
通過設置Camera.PreviewCallback來取得預覽數據。
import java.io.IOException;
import android.content.Context;
import android.content.res.Configuration;
import android.graphics.SurfaceTexture;
import android.hardware.Camera;
import android.util.Log;
import android.view.TextureView;
/**
* camera預覽視圖
* Created by on 2020/2/26.
*/
public class CameraPreview extends TextureView implements TextureView.SurfaceTextureListener {
private static final String TAG = "CameraPreview";
private Camera mCamera;
public CameraPreview(Context context) {
super(context);
}
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;
}
public void setCamera(Camera camera) {
this.mCamera = camera;
}
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
Log.d(TAG, "TextureView onSurfaceTextureAvailable");
if (this.getResources().getConfiguration().orientation != Configuration.ORIENTATION_LANDSCAPE) {
mCamera.setDisplayOrientation(90);
} else {
mCamera.setDisplayOrientation(0);
}
try {
mCamera.setPreviewCallback(mCameraPreviewCallback);
mCamera.setPreviewTexture(surface); // 使用SurfaceTexture
mCamera.startPreview();
} catch (IOException ioe) {
// Something bad happened
}
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
Log.d(TAG, "TextureView onSurfaceTextureSizeChanged"); // Ignored, Camera does all the work for us
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
Log.d(TAG, "TextureView onSurfaceTextureDestroyed");
mCamera.stopPreview();
mCamera.release();
return true;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture surface) {
}
private Camera.PreviewCallback mCameraPreviewCallback = new Camera.PreviewCallback() {
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
Log.d(TAG, "onPreviewFrame: data.length=" + data.length);
}
};
}
操作界面TextureAct。獲取camera操作權,初始化CameraPreview並添加到佈局中。第一次獲取camera時在子線程中操作。
在onPause中釋放camera,onResume中嘗試取回camera控制權。這樣應用暫時退回後臺時,其他應用可以操作攝像頭
public class TextureAct extends AppCompatActivity {
private static final String TAG = "TextureAct";
private Camera mCamera;
private CameraPreview mPreview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_texture);
new InitCameraThread().start();
}
@Override
protected void onResume() {
if (null == mCamera) {
if (safeCameraOpen()) {
mPreview.setCamera(mCamera); // 重新獲取camera操作權
} else {
Log.e(TAG, "無法操作camera");
}
}
super.onResume();
}
@Override
protected void onPause() {
super.onPause();
releaseCamera();
}
@Override
protected void onDestroy() {
super.onDestroy();
releaseCamera();
}
private boolean safeCameraOpen() {
boolean qOpened = false;
try {
releaseCamera();
mCamera = Camera.open();
qOpened = (mCamera != null);
} catch (Exception e) {
Log.e(TAG, "打開相機失敗");
e.printStackTrace();
}
return qOpened;
}
private void releaseCamera() {
if (mCamera != null) {
mCamera.setPreviewCallback(null);
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}
private class InitCameraThread extends Thread {
@Override
public void run() {
super.run();
if (safeCameraOpen()) {
Log.d(TAG, "TextureAct 開啓攝像頭");
runOnUiThread(new Runnable() {
@Override
public void run() {
mPreview = new CameraPreview(TextureAct.this, mCamera);
mPreview.setSurfaceTextureListener(mPreview);
FrameLayout preview = findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
});
}
}
}
}
-
Textureview必須在硬件加速開啓的窗口中使用。android:hardwareAccelerated=“true” 默認的這個屬性就是true,無需再設置。
-
每接到一幀數據,就會調用一次onSurfaceTextureUpdated()。通過這個接口。能夠將上來的SurfaceTexture送給OpenGL再去處理。