简介

因工作原因要学习Android的Camera预览功能，这个DEMO有两个Activity，使用Camera库实现

项目地址https://github.com/haowenlai2008/CameraPreview
代码参考了这个老哥https://dotblogs.com.tw/alonstar/2011/06/08/android_camera

Camera预览使用SurfaceView和Camera类，让它们两个联系起来并开启预览的比较关键的代码：

mCamera.setPreviewDisplay(mSurfaceHolder);mCamera.startPreview();

其实就是这两行，把SurfaceView的holder设置到Camera上，开启预览就OK了

最关键的两个工作

设置SurfaceView的回调

private void initView() {        surfaceView = findViewById(R.id.surfaceView);        mSurfaceHolder = surfaceView.getHolder();        mSurfaceHolder.addCallback(this);    }

让当前Activity实现Surface.Callback接口，让mSurfaceHolder绑定当前Activity作为回调

    @Override    public void surfaceCreated(SurfaceHolder surfaceHolder) {        //检查权限        if (ContextCompat.checkSelfPermission(TestActivity.this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {        } else {            CameraOpen();        }    }    @Override    public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {        Camera.Parameters parameters = mCamera.getParameters();        parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);        mCamera.setParameters(parameters);        mCamera.startPreview();    }    @Override    public void surfaceDestroyed(SurfaceHolder surfaceHolder) {        mCamera.stopPreview();        mCamera.release();        mCamera = null;    }

绑定SurfaceView的Holder到Camera

//打开照相机    public void CameraOpen() {        try        {            mCamera = Camera.open(cameraId);            mCamera.setDisplayOrientation(90);            mCamera.setPreviewDisplay(mSurfaceHolder);            mCamera.startPreview();        } catch (IOException e) {            mCamera.release();            mCamera = null;            Toast.makeText(TestActivity.this, "surface created failed", Toast.LENGTH_SHORT).show();        }    }

预览界面代码

package com.example.test;import android.Manifest;import android.app.Activity;import android.content.Intent;import android.content.pm.ActivityInfo;import android.content.pm.PackageManager;import android.hardware.Camera;import android.os.Bundle;import android.view.SurfaceHolder;import android.view.SurfaceView;import android.view.View;import android.view.Window;import android.widget.Button;import android.widget.Toast;import androidx.core.content.ContextCompat;import java.io.IOException;public class TestActivity extends Activity implements  SurfaceHolder.Callback{    public Button mButton;    public Button switchBtn;    private Camera mCamera;    private SurfaceView surfaceView;    private SurfaceHolder mSurfaceHolder;    private int cameraId = 1;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.test_layour);        this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);        initView();        initButton();    }    //视图初始化    private void initView() {        surfaceView = findViewById(R.id.surfaceView);//获得SurfaceView的实例        mSurfaceHolder = surfaceView.getHolder();//获得SurfaceView的Holder        mSurfaceHolder.addCallback(this);//设置Holder的回调    }    //打开照相机    public void CameraOpen() {        try        {            //打开摄像机            mCamera = Camera.open(cameraId);            mCamera.setDisplayOrientation(90);            //绑定Surface并开启预览            mCamera.setPreviewDisplay(mSurfaceHolder);            mCamera.startPreview();        } catch (IOException e) {            mCamera.release();            mCamera = null;            Toast.makeText(TestActivity.this, "surface created failed", Toast.LENGTH_SHORT).show();        }    }    //回调初始化    private void initButton() {        //返回上个界面的按钮        mButton = findViewById(R.id.button2);        mButton.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                Intent intent = new Intent();                intent.setClass(TestActivity.this, MainActivity.class);                startActivity(intent);            }        });        //翻转摄像机的按钮        switchBtn = findViewById(R.id.button3);        switchBtn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                CameraSwitch();            }        });    }    @Override    public void surfaceCreated(SurfaceHolder surfaceHolder) {        //检查权限        if (ContextCompat.checkSelfPermission(TestActivity.this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {        } else {            CameraOpen();        }    }    @Override    public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {        Camera.Parameters parameters = mCamera.getParameters();        parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);        mCamera.setParameters(parameters);        mCamera.startPreview();    }    @Override    public void surfaceDestroyed(SurfaceHolder surfaceHolder) {        mCamera.stopPreview();        mCamera.release();        mCamera = null;    }    //翻转摄像机    public void CameraSwitch()    {        cameraId = cameraId == 1 ? 0 : 1;        mCamera.stopPreview();        mCamera.release();        mCamera = null;        CameraOpen();    }}

思路很简单，在Surface创建的回调中去打开摄像机并开启摄像机的预览，至于为什么我要使用两个Activity，原因是开启摄像机需要获得权限，如果在打开照相机的Activity请求权限的话，会跳到请求权限成功的回调所在的线程导致照相机打不开。

预览页面的UI布局

<?xml version="1.0" encoding="utf-8"?>

Android(安卓)Camera预览

简介

最关键的两个工作

预览界面代码

预览页面的UI布局

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