Kotlin ContentProvider使用方法详解

2022-12-08 20:53

短信预约 -IT技能 免费直播动态提醒

android的四大组件，已经介绍了两个，这一节介绍ContentProvider。前面的广播可以进行 app内的通讯，如果需要进行app之间的通讯，在android 中使用的是ContentProvider。ContentProvider 也分为三种，一，作为数据的存储和查询，也就是别人来调用你ContentProvider。二，调用者ContentResolver ，用来调用插入和查询数据。三，观察者ContentObserver ,比如监控短信的变化。

ContentProvider提供者

ContentProvider 提供者作为一个母体，用来通过数据的查询和插入，这样做的好处是，让每个服务都相互独立，而且有可以像外部提供相应的接口。比如通讯录，短信息等。他们作为一种服务，根据用户的权限来提供特有的服务。

这里我们也建立一个ContentProvider ，用户可以来调用，提供查询和插入的功能。我们用sqlite对数据进行存储和查询。

    inner class DBHelper(context:Context,name:String,
                         factory:SQLiteDatabase.CursorFactory?,version:Int):SQLiteOpenHelper(context,name,factory, version){
        override fun onCreate(_db: SQLiteDatabase?) {
            var sql:String = "CREATE TABLE " + DATUM_TABLE_NAME +
                    " (" + "_id INTEGER PRIMARY KEY AUTOINCREMENT," +
                    Constants.TEXT+
                    " VARCHAR(20)" + ")"
            _db?.execSQL(sql)
        }
        override fun onUpgrade(_db: SQLiteDatabase?, p1: Int, p2: Int) {
            var sql:String = "DROP TABLE IF EXISTS " + DATUM_TABLE_NAME
            _db?.execSQL(sql)
            onCreate(_db)
        }
    }

创建 ContentProvider

class DataProvider : ContentProvider()

实现两个接口 query，insert。

    override fun query(
        uri: Uri,
        p: Array<out String>?,
        s: String?,
        args: Array<out String>?,
        sort: String?
    ): Cursor? {
        val qb = SQLiteQueryBuilder()
        qb.tables = DATUM_TABLE_NAME
        qb.projectionMap = projMap
        var s1 = s
        if (sUriMatcher.match(uri) != DATUM) {
            if (sUriMatcher.match(uri) == DATUM_ID)
                s1 = s + "_id = " + uri?.lastPathSegment
            else
                throw IllegalArgumentException("Unknown URI " + uri)
        }
        val db = dbHelper?.readableDatabase
        val c = qb.query(db, p, s1, args, null, null, sort)
        c.setNotificationUri(context?.contentResolver ?: null, uri)
        return c
    }

insert 接口

   override fun insert(uri: Uri, cv: ContentValues?): Uri? {
        var m:Int = sUriMatcher.match(uri).toInt()
        m = 1
        if (m != 1){
            throw IllegalArgumentException("Unknown URI " + uri)
        }
        val v: ContentValues
        if (cv != null)
            v = ContentValues(cv)
        else
            v = ContentValues()
        val db = dbHelper?.writableDatabase
        val rId = db?.insert(DATUM_TABLE_NAME, Constants.TEXT, v)
        if (rId != null) {
            if (rId > 0) {
                val uri = ContentUris.withAppendedId(Constants.URL, rId)
                context?.contentResolver?.notifyChange(uri, null)
                return uri
            }
        } else {
            throw SQLException("Failed to insert row into " + uri)
        }
        return null
    }

如何调用呢？

        var textView = findViewById<TextView>(R.id.textView)
        var btn = findViewById<Button>(R.id.btn)
        // Inserting data into content provider
        val tuple = ContentValues()
        tuple.put(Constants.TEXT, Constants.TEXT_DATA)
        contentResolver.insert(Constants.URL, tuple)
        // Reading from content provider
        val cols = arrayOf(Constants.ID, Constants.TEXT)
        val u = Constants.URL
        val c = contentResolver.query(u, cols, null, null, null)
        if (c!!.moveToLast())
            textView.text = "Data read from content provider: " +
                    c!!.getString(c.getColumnIndex(Constants.TEXT))
        else
            textView.text = "Access denied"

在AndroidManifest.xml 上添加：

        <provider
            android:name="com.kotlin.kotlin_start_ch16.DataProvider"
            android:authorities="com.kotlin.kotlin_start_ch16.provider"
            android:exported="true"
            android:multiprocess="true"/>

模拟插入数据后，对数据进行查询，并显示在textview上。

contentResolver获取短信数据

app获取短信需要相应的权限，首先要确认和申请权限。在AndroidManifest.xml 上添加，

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

这样还不够，需要进行权限的用户授权。

fun checkPermission():Boolean{
        var result = ContextCompat.checkSelfPermission(applicationContext,Manifest.permission.READ_SMS)
        return result==PackageManager.PERMISSION_GRANTED
    }
    fun requestPermission(i:Int){
        ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.READ_SMS),i)
    }
    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    }

当用户确认以后，才可以进行短信的获取。

        if (!checkPermission()){
            requestPermission(123)
        }
        btn.setOnClickListener {
            val cols = arrayOf("_id","address","date","type","body")
            var c = contentResolver.query(Uri.parse("content://sms/"),cols,null,null, null)
            while (c!!.moveToNext()){
                var body=c.getString(4)
                textView.text = body
                var s = SmsInfo(c.getInt(0),c.getString(1),c.getLong(2),c.getString(4))
                sms.add(s)
            }
            var text:String = ""
            sms.forEach{
                text = text + it.address + "\n"
                text = text + it.info + "\n"
            }
            textView.text = text
        }

ContentObserver监控短信的到来

ContentObserver监控短信同样的需要相应的权限，可以看看上节的代码，要监控短信需要新建一个类继承ContentObserver，并进行注册：

            smsContentObserver = SmsContentObserver(this, Handler(Looper.getMainLooper()), conversationsHandler)
            //smsContentObserver = SmsContentObserver(this, Handler(Looper.getMainLooper()))
            smsContentObserver?.let {
                //it.start()
                contentResolver.registerContentObserver(Telephony.Sms.CONTENT_URI, true, it)
                contentResolver.registerContentObserver(Telephony.Mms.CONTENT_URI, true, it)
                contentResolver.registerContentObserver(Telephony.MmsSms.CONTENT_URI, true, it)
            }

收到短信后，对短信进行处理：

    private fun newSms() {
        val newSms: Map<Int, SmsObject> = smsDeleteDetector.newSms()
        newSms.forEach {
            if ((it.value._type).toInt() == Telephony.Sms.Inbox.MESSAGE_TYPE_INBOX) {
                logToastHelper.showLogMsg(
                    context,
                    "$tag Inbox ID:${it.value._id}  ThreadId:${it.value._threadId} ",
                    "SMS From ${it.value._address} : ${it.value._body}"
                )
            } else if (((it.value._type).toInt()) == Telephony.Sms.Inbox.MESSAGE_TYPE_SENT) {
                logToastHelper.showLogMsg(
                    context,
                    "$tag Outbox ID:${it.value._id}  ThreadId:${it.value._threadId}",
                    "SMS Sent To ${it.value._address} : ${it.value._body}"
                )
            }
        }
    }