android读取相机内容与引用摄像头

引用摄像头

package com.example.myapplication

import android.app.Activity
import android.content.Intent
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.graphics.Matrix
import android.media.ExifInterface
import android.net.Uri
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.provider.MediaStore
import kotlinx.android.synthetic.main.activity_main.*
import androidx.core.content.FileProvider
import java.io.File

class MainActivity : AppCompatActivity() {
    val takePhoto = 1
    lateinit var imageUri: Uri
    lateinit var outputImage: File
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        //拍照按钮，点击事件侦听
        takePhotoBtn.setOnClickListener {
            //创建File对象，用于存储拍照后的图片
            outputImage = File(externalCacheDir, "output_image.jpg") //存放照片
            //如果文件存在则进行删除
            if (outputImage.exists()) {
                outputImage.delete()
            }
            //创建新的对象
            outputImage.createNewFile()
            //获取图片uri
            imageUri = FileProvider.getUriForFile(this, "com.example.myapplication3.fileprovider", outputImage)

            //启动相机并获取拍的照片作为活动返回对象
            val intent = Intent(MediaStore.ACTION_IMAGE_CAPTURE) //设置相片输出保存的Uri路径
            intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri)  //指定图片的输出地址
            startActivityForResult(intent, takePhoto) //takePhoto为标记代码
        }
    }

    //对返回的照片进行处理
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data) //Intent返回结果处理，显示照片
        when (requestCode) {//匹配Code
            takePhoto -> {
                if (resultCode == Activity.RESULT_OK) { //✔键
                    val bitmap = BitmapFactory.decodeStream(contentResolver.openInputStream(imageUri))
                    imageView.setImageBitmap(rotateIfRequired(bitmap))
                }
            }
        }
    }

    //同步图片方向
    private fun rotateIfRequired(bitmap: Bitmap): Bitmap { //确保物理设备旋转时获取的照片跟着旋转
        val exif = ExifInterface(outputImage.path) //ExifInterface接口获得图片方向
        val orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL)
        return when (orientation) { //按获得方向进行旋转
            ExifInterface.ORIENTATION_ROTATE_90 -> rotateBitmap(bitmap, 90)
            ExifInterface.ORIENTATION_ROTATE_180 -> rotateBitmap(bitmap, 180)
            ExifInterface.ORIENTATION_ROTATE_270 -> rotateBitmap(bitmap, 270)
            else -> bitmap
        }
    }

    //旋转图片
    private fun rotateBitmap(bitmap: Bitmap, degree: Int): Bitmap { //用角度做参数，设置旋转规则
        val matrix = Matrix()
        matrix.postRotate(degree.toFloat()) //创建经过旋转后的新图片
        val rotateBitmap =
            Bitmap.createBitmap(bitmap, 0, 0, bitmap.width, bitmap.height, matrix, true)
        bitmap.recycle() //将不需要的旧图片对象回收
        return rotateBitmap
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.myapplication">
    <uses-permission android:name="android.permission. WRITE_EXTERNAL_STORAGE" />
    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:requestLegacyExternalStorage="true"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.MyApplication"
        tools:targetApi="31">
        <provider
            android:name="androidx.core.content.FileProvider"
            android:authorities="com.example.myapplication3.fileprovider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths"/>
        </provider>
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

注意17-25行，其中android:authorities的值必须与Activity类中第35行的值相同

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/takePhotoBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Take Photo" />
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="my_images" path="/"/>
</paths>

将图片存储在数据库中（图片压缩成ByteArray）

val baos = ByteArrayOutputStream()
bitmap.compress(Bitmap.CompressFormat.PNG,100,baos) //对bitmap进行格式转发成PNG
val args = arrayOf<Any>(baos.toByteArray())
val db = dbHelper.writableDatabase
val id = "1712131536"
val insertPhoto = "update user set photo = ? where id='${id}'"
db.execSQL(insertPhoto, args)

注意：execSQL第二个参数不能套arraysOf（）

读取数据库中的ByteArray转化成图片

val db = dbHelper.readableDatabase
val cursor = db.query("user", arrayOf("photo"),"id=?", arrayOf("1712131536"),"","","")
if (cursor!=null&&cursor.moveToFirst()){
    val photo = cursor.getBlob(cursor.getColumnIndex("photo"))
    if(photo!=null){
        val bais = ByteArrayInputStream(photo)
        imageView.setImageDrawable(Drawable.createFromStream(bais,"photo"))
    }
}

相关链接：www.cnblogs.com/MMLoveMeMM/…

读取相机内容

val intent = Intent(Intent.ACTION_OPEN_DOCUMENT)
intent.addCategory(Intent.CATEGORY_OPENABLE) //指定只显示图片
intent.type = "image/*"
startActivityForResult(intent, fromAlbum)

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data) //Intent返回结果处理，显示照片
        when (requestCode) {//匹配Code
            fromAlbum -> {
                if (resultCode == Activity.RESULT_OK && data != null) {
                    data.data?.let { uri ->//将选择的图片显示
                        val bitmap = contentResolver.openFileDescriptor(uri,"r")?.use {
                            BitmapFactory.decodeFileDescriptor(it.fileDescriptor)
                        }
                        val baos = ByteArrayOutputStream()
                        bitmap?.compress(Bitmap.CompressFormat.PNG,100,baos) //对bitmap进行格式转发成PNG
                        val args = arrayOf<Any>(baos.toByteArray())
                        val db = dbHelper.writableDatabase
                        val account = User.account
                        val insertPhoto = "update user set photo = ? where account='${account}'"
                        db.execSQL(insertPhoto, args)
                        userImage.setImageBitmap(bitmap)
                    }
                }
            }
        }
    }