Content provider

  • It is mainly used to realize data sharing between different applications
  • You can choose which part of the data to share only
  • Use existing content providers to read and manipulate data in programs
  • Or create your own content provider to provide external access to our program’s data

Runtime permissions

mechanism

  • Common Rights The system automatically grants permissions
  • Dangerous permissions (permissions group name | permissions)
    • CALENDAR: READ_CALENDAR / WRITE_CALENDAR
    • CAMERA: CAMERA
    • CONTACTS: READ_CONTACTS / WRITE_CONTACTS / GET_CONTACTS
    • LOCATION: ACCESS_FINE_LOCATION / ACCESS_COARSE_LOCATION
    • MICROPHONE: RECORD_AUDIO
    • PHONE: READ_PHONE_STATE / CALL_PHONE / READ_CALL_LOG / WRITE_CALL_LOG / ADD_VOICEMAIL / USE_SIP / PROCESS_OUTGOING_CALLS
    • SENSORS: BODY_SENSORS
    • SMS: SEND_SMS / RECEIVE_SMS / READ_SMS / RECEIVE_WAP_PUSH / REACEIVE_MMS
    • STORAGE: READ_EXTERNAL_STORAGE / WRITE_EXTERNAL_STORAGE
    • After a dangerous permission is granted, all other permissions in the corresponding permission group are also granted

Request permission at runtime

  • Declare in the androidmanifest.xml file

    <uses-permission android:name="android.permission.CALL_PHONE" />
  • @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button makeCall = findViewById(R.id.make_call); makeCall.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (ContextCompat.checkSelfPermission((MainActivity.this, Manifest.permission.CALL_PHONE) ! = PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions(MainActivity.this, new String[] { Manifest.permission.CALL_PHONE }, 1); } else { call(); }}}); } private void call() { try { Intent intent = new Intent(Intent.ACTION_CALL); intent.setData(Uri.parse("tel:10086")); startActivity(intent); } catch (SecurityException e) { e.printStackTrace(); } } @Override public void onRequestPermissionResult(int requestCode, String[] permissions, int[] grantResults) { switch (requestCode) { case 1: if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { call(); } else { Toast.makeText(this, "You denied the permission", Toast.LENGTH_SHORT).show(); } break; default: } }Copy the code
    • ContextCompat.checkSelfPermission: Check whether the user is authorized

      The first argument is Context

      The second parameter is the specific permission name

      With the return values andPackageManager.PERMISSION_GRANTEDCompare, equal is authorized, unequal is not authorized
    • If not authorized, it is calledActivityCompat.requestPermissions()Apply for authorization from a user

      The first parameter requires an instance of Acitivity

      The second argument is an array of strings containing the names of the permissions to apply for

      The third parameter is the request code, as long as it is unique
    • Call outActivityCompat.requestPermissions()A dialog box is displayed asking you to apply for permission

      After the user chooses to agree or reject, callback toonRequestPermissionResultIn the method

      The result of authorization is encapsulated ingrantResultsIn the parameters
    • Make a phone call
      • Build an implicit Intent action named intent.action_call, which is the built-in action for making a call. The data section specifies the protocol tel and the number 10086
      • ACTION_DIAL Indicates that the dialing interface is opened. You do not need to declare the permission for the Intent

Access data in other programs

Basic usage of ContentResolver

  • Through the ContextgetContentResolver()Method to get an instance of the class
  • A series of methods are provided for CRUD operations on data

    insert() update() delete() query()
  • Content URI: Establishes a unique identifier for data in a content provider
    • authority: Distinguish between different applications, generally adopted<package_name>.providerIs named in a way
    • path: Distinguishes different tables in the same application, usually added toauthoritybehind
    • Prefixes the string with a protocol declaration
    • E.g. content://com.example.app.provider/table1
    • Resolve toUriobject

      Uri uri = Uri.parse(content://com.example.app.provider/table1);
  • The queryquery(): 
    Cursor cursor = getContentResolver().query(
    uri,
    projection,
    selection,
    selectionArgs,
    sortOrder);
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    • uri: Specifies a table under an application to be queried
    • projection: Specifies the column name to be queried
    • selection: Specifies where constraints
    • selectionArgs: provides concrete values for placeholders in where
    • sortOrder: Specifies the sorting method of the query results
    if (cursor ! = null) { while (cursor.moveToNext()) { String column1 = cursor.getString(cursor.getColumnIndex("column1")); int column2 = cusor.getInt(cursor.getColumnIndex("column2")); } cursor.close() }Copy the code
    • The move cursor traverses all rows and retrieves the data for the corresponding column in each row
  • addinsert() 
    ContentValue values = new ContentValues();
values.put("column1", "text");
values.put("column2", 1);
getContentResolver().insert(uri, values);
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  • Modify theupdate() 
    ContentValues values = new ContentValues(); values.put("column1", ""); getContentResolver().update(uri, values, "column1 = ? and column2 = ?" , new String[] {"text", "1"});Copy the code
  • deletedelete() 
    getContentResolver().delete(uri, "column2 = ?", new String[] { "1" });
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Create your own content provider

Create a step

  • Create a new class inheritanceContentProvider

    Override six abstract methods
    • boolean onCreate()
      • Called when the content provider is initialized, usually to complete operations such as creating and upgrading the database
      • It is initialized only if a ContentResolver attempts to access data in the program
    • Cursor query(Uri uri, String[] projection, String selection, String[] SelectionArgs, String sortOrder)
      • The results of the query are stored in the Cursor object and returned
    • Uri insert(Uri uri, ContentValues values)
      • Returns a URI that represents the new record
    • int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)
      • Returns the number of affected rows
    • int delete(Uri uri, String selection, String[] selectionArgs)
      • Returns the number of deleted rows
    • String getType(Uri uri)
      • Return the correspondingMIMEtype
      • MIMEThe string consists of three parts
        • Have to bevndAt the beginning
        • If the content URI ends in a path, it is followedandroid.cursor.dir/

          If the content URI ends in id, it is followedandroid.cursor.item/
        • The last plug invnd.<authority>.<path>
        • E.g. vnd.android.cursor.dir/vnd.com.example.app.provide.table1

The content URI

  • Establishes a unique identifier for the data in the content provider
  • authority: Distinguish between different applications, generally adopted<package_name>.providerIs named in a way
  • path: Distinguishes different tables in the same application, usually added toauthoritybehind
  • Prefixes the string with a protocol declaration
  • You can add an ID after the content URI

    content://com.example.app.provider/table1/1
    • Select * from table1 where com.example.app = com.example.app
  • Wildcard matches can be used
    • *Matches any character of any length
    • #Matches a number of any length
    • E.g. content://com.example.app.provider/*Matches the contents of any table

      content://com.example.app.provider/table1/#Matches any row in table1
  • UriMatcherclass
    • provideaddURI()methods

      Accepts 3 parameters, which can be passed in separatelyauthority,pathAnd a child can take code
    • callmatch()You can pass in a Uri object and return some custom code that matches the Uri object

      Use this code to determine which table data needs to be accessed
  • All CRUD operations must match the URI format of the corresponding content to prevent privacy data leakage
public class MyProvider extends ContentProvider { public static final int TABLE1_DIR = 0; public static final int TABLE1_ITEM = 1; public static final int TABLE2_DIR = 2; public static final int TABLE2_ITEM = 3; private static UriMatcher uriMatcher; static { uriMatcher = new UriMatcher(UriMatcher.NO_MATCH); uriMatcher.addURI("com.example.app.provider", "table1", TABLE1_DIR); uriMatcher.addURI("com.example.app.provider", "table1/#", TABLE1_ITEM); uriMatcher.addURI("com.example.app.provider", "table2", TABLE1_DIR); uriMatcher.addURI("com.example.app.provider", "table2/#", TABLE2_ITEM); }... public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {switch (urimatcher.match (uri)) {case TABLE1_DIR: // Query all data breaks in table1; Case TABLE1_ITEM: // Select break from table2; Case TABLE2_DIR: // query all data breaks in table2; Case TABLE2_ITEM: // Select break from table2; default: break; }... } @Override public String getType(Uri uri) { switch (uriMathcer.match(uri)) { case TABLE1_DIR: return "vnd.android.cursor.dir/vnd.com.example.app.provide.table1"; case TABLE1_ITEM: return "vnd.android.cursor.item/vnd.com.example.app.provide.table1"; case TABLE2_DIR: return "vnd.android.cursor.dir/vnd.com.example.app.provide.table2"; case TABLE2_ITEM: return "vnd.android.cursor.item/vnd.com.example.app.provide.table2"; default: break; } return null; }... }Copy the code