写一个简单的例子，实现一个常见的开发功能：拍照功能。
技术路线：通过TextureView的通道获取SurfaceTexture作为相机的预览，然后通过Camera的take方法把相机抓取的byte字节数据转换为Bitmap，然后存放到手机的存储器上，至此，一个最简单的拍照功能完成。
注意，本例如果运行在Android高版本（6.0+，7.0+或更高），需要多写运行时权限申请代码。本例出于功能演示，不再冗余的写这部分代码。只给出最骨干的关键代码逻辑。

布局文件activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/holo_blue_light"
    tools:context="zhangphil.view.MainActivity">

    <zhangphil.view.MyTextureView
        android:id="@+id/textureView"
        android:layout_width="300dp"
        android:layout_height="200dp"
        android:layout_centerInParent="true" />

    <Button
        android:id="@+id/capture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="拍摄" />
</RelativeLayout>

MyTextureView.java：

package zhangphil.view;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.SurfaceTexture;
import android.hardware.Camera;
import android.os.Environment;
import android.util.AttributeSet;
import android.util.Log;
import android.view.TextureView;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;

/**
 * Created by Phil on 2017/9/13.
 */

public class MyTextureView extends TextureView {
    public Camera mCamera;

    public MyTextureView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        mCamera = Camera.open();

        this.setSurfaceTextureListener(new SurfaceTextureListener() {

            @Override
            public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int width, int height) {
                try {
                    mCamera.setPreviewTexture(surfaceTexture);
                    mCamera.startPreview();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int width, int height) {

            }

            @Override
            public boolean onSurfaceTextureDestroyed(SurfaceTexture surfaceTexture) {
                mCamera.stopPreview();
                mCamera.release();
                mCamera = null;

                return true;
            }

            @Override
            public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {

            }
        });
    }

    public void take() {
        if(mCamera!=null)
            mCamera.takePicture(null, null, mPictureCallback);
    }

    Camera.PictureCallback mPictureCallback = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            mCamera.stopPreview();
            new FileSaver(data).save();
        }
    };

    private class FileSaver implements Runnable {
        private byte[] buffer;

        public FileSaver(byte[] buffer) {
            this.buffer = buffer;
        }

        public void save() {
            new Thread(this).start();
        }

        @Override
        public void run() {
            try {
                File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM), "zhangphil.png");
                file.createNewFile();

                FileOutputStream os = new FileOutputStream(file);
                BufferedOutputStream bos = new BufferedOutputStream(os);

                Bitmap bitmap = BitmapFactory.decodeByteArray(buffer, 0, buffer.length);
                bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);

                bos.flush();
                bos.close();
                os.close();

                Log.d("照片已保存", file.getAbsolutePath());

                mCamera.startPreview();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

MainActivity.java：

package zhangphil.view;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {
    private MyTextureView textureView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textureView = (MyTextureView) findViewById(R.id.textureView);
        findViewById(R.id.capture).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                textureView.take();
            }
        });
    }
}

权限：

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

代码运行结果：