Android 如何切换前后摄像头

在Android自定义相机开发中,切换前置摄像头可能会遇到一些问题,如预览尺寸设置不当导致黑屏。关键在于正确获取并设置前置摄像头支持的预览尺寸,以及根据设备方向调整预览方向。此外,错误的代码可能导致摄像头锁死,这时可能需要重启手机解决。本文基于APIDemo提供了解决方案。

最近开发自定义相机,其中前置摄像头的调用让我搞了好久,网上千篇一律的文章实在让人作呕,而且没一个可以成功调用前置摄像头的。在朋友的提示下,看了下系统的APIDemo,根据这个demo修改后如下。


package cn.fotomen.camera.activity;

import android.app.Activity;
import android.hardware.Camera;
import android.hardware.Camera.CameraInfo;
import android.hardware.Camera.Size;
import android.os.Bundle;
import android.util.Log;
import android.view.*;
import android.widget.Button;
import cn.fotomen.camera.R;
import cn.fotomen.camera.model.Util;
import java.io.IOException;
import java.util.List;

public class CameraPreview extends Activity implements SurfaceHolder.Callback, View.OnClickListener {
    private static final String TAG = "CameraPreview";
    //private Preview mPreview;
    Camera mCamera;
    private SurfaceView mSurfaceView;
    private SurfaceHolder mHolder;
    int numberOfCameras;
    int cameraCurrentlyLocked;
    Size mPreviewSize;
    List<Size> mSupportedPreviewSizes;
    // The first rear facing camera
    int defaultCameraId;
    private Button bt_switch;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
      
android调用camera时,可以自己写一个activity,赋上相关参数,打开前camera就可以了; 需要申请的permission,在AndroidManifest.xml中添加: 主要功能,打开前camera private Camera openFrontFacingCameraGingerbread() { int cameraCount = 0; Camera cam = null; Camera.CameraInfo cameraInfo = new Camera.CameraInfo(); cameraCount = Camera.getNumberOfCameras(); for (int camIdx = 0; camIdx < cameraCount; camIdx++) { Camera.getCameraInfo(camIdx, cameraInfo); if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) { try { cam = Camera.open(camIdx); mCurrentCamIndex = camIdx; } catch (RuntimeException e) { Log.e(TAG, "Camera failed to open: " + e.getLocalizedMessage()); } } } return cam; } 根据打开时的横竖屏方向来调整preview角度 //根据横竖屏自动调节preview方向,Starting from API level 14, this method can be called when preview is active. private static void setCameraDisplayOrientation(Activity activity,int cameraId, Camera camera) { Camera.CameraInfo info = new Camera.CameraInfo(); Camera.getCameraInfo(cameraId, info); int rotation = activity.getWindowManager().getDefaultDisplay().getRotation(); //degrees the angle that the picture will be rotated clockwise. Valid values are 0, 90, 180, and 270. //The starting position is 0 (landscape). int degrees = 0; switch (rotation) { case Surface.ROTATION_0: degrees = 0; break; case Surface.ROTATION_90: degrees = 90; break; case Surface.ROTATION_180: degrees = 180; break; case Surface.ROTATION_270: degrees = 270; break; } int result; if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) { result = (info.orientation + degrees) % 360; result = (360 - result) % 360; // compensate the mirror } else { // back-facing result = (info.orientation - degrees + 360) % 360; } camera.setDisplayOrientation(result); }
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