ContentProvider是Android的四大組件的成員，它能為數(shù)據(jù)提供外部訪問接口啤月，即其他應(yīng)用也能訪問到該應(yīng)用的數(shù)據(jù)品腹，類似于共享的數(shù)據(jù)庫苦银。
ContentProvider
常見用法
- 通過其他應(yīng)用的ContentProvider訪問其應(yīng)用數(shù)據(jù)
- 創(chuàng)建本地的ContentProvider為其他應(yīng)用提供數(shù)據(jù)訪問服務(wù)
訪問聯(lián)系人的數(shù)據(jù)
首先添加幾個聯(lián)系人姻灶，我國著名詩人-->李白杜甫
聯(lián)系人
讀取聯(lián)系人數(shù)據(jù)
由于Android6.0以上讀取聯(lián)系人需要申請權(quán)限，所以我們先在Manifest中添加好權(quán)限
<uses-permission android:name="android.permission.READ_CONTACTS" />
然后還需要在Activity中進行權(quán)限的申請
這里要注意Manifest中的權(quán)限要和Activity中的權(quán)限一致
由于我之前在Activity中申請的權(quán)限是Manifest.permission_group.CONTACTS
然后進入應(yīng)用的時候老是彈出no permission的Toast
兩個地方的權(quán)限不一致的話诈茧，系統(tǒng)會默認(rèn)拒絕該權(quán)限的申請产喉，然后我為此折騰了半天...
//檢查是否有讀取聯(lián)系人的權(quán)限
int hasPermission = ContextCompat.checkSelfPermission(this, Manifest.permission.READ_CONTACTS);
if (hasPermission == PackageManager.PERMISSION_DENIED) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_CONTACTS}, REQUEST_CODE_CONTRACTS);
} else {
//這里進行讀取聯(lián)系人的數(shù)據(jù)
read();
}
//-----------------------------------分界線------------------------------------//
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
if (requestCode == REQUEST_CODE_CONTRACTS) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
read();
} else {
Toast.makeText(this, "no permission", Toast.LENGTH_SHORT).show();
}
}
}
讀取聯(lián)系人給的外部數(shù)據(jù)接口需要用到ContentReslover類
- 通過Context.getContentReslover獲取ContentReslover
- 調(diào)用ContentReslover的查詢方法query
- 通過Cursor一步一步的把數(shù)據(jù)傳入ArrayList中
private void read() {
Cursor cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);
if (cursor != null) {
while (cursor.moveToNext()) {
String name = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
String number = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
//這就是ListView的數(shù)據(jù)源-->contacts
contacts.add(name + ": " + number);
}
cursor.close();
}
}
然后通過ListView展示出讀取的數(shù)據(jù)
image.png
創(chuàng)建自己的內(nèi)容提供器
其實ContentProvider的操作跟SQLiteDatabase差不多的
新建一個繼承自ContentProvider的類-->StudentProvider，實現(xiàn)如下方法：
- onCreate：
- insert
- delete
- update
- query
- getType
- getType方法是獲取Uri對象對應(yīng)的MIME類型(類似于ID吧)
- contentProvider中的任意表對應(yīng)就是"vnd.android.cursor"+"dir"+"/vnd."+authorities+表名
- 表中任意的數(shù)據(jù)對應(yīng)"vnd.android.cursor"+"item"+"/vnd."+authorities+表名
- 也就一個地方不同敢会，dir和item的區(qū)別
<provider
android:name=".lesson6.StudentProvider"
android:authorities="org.fourstars.firstcode.provider"
android:enabled="true"
android:exported="true">
</provider>
注意清單文件中的authorities要和Activity中的AUTHORITY一致
因為ContentProvider是通過Uri來訪問數(shù)據(jù)的曾沈，我們使用UriMatcher來匹配到合適的uri
URI的標(biāo)準(zhǔn)寫法
content://+authorities+表名
在authorities后加入"/*"，如 content://ort.fourstars.firstcode.provider/ * 就能匹配到任意表
在authorities后加入"表名/#"鸥昏，就能匹配到表中的任意數(shù)據(jù)
public class StudentProvider extends ContentProvider {
public static final int STUDENT_DIR = 1111;
public static final int STUDENT_ITEM = 1110;
public static final String AUTHORITY = "ort.fourstars.firstcode.provider";
private static UriMatcher uriMatcher;
private DbHelper dbHelper;
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(AUTHORITY, "student", STUDENT_DIR);
uriMatcher.addURI(AUTHORITY, "student/#", STUDENT_ITEM);
}
public StudentProvider() {
}
@Override
public boolean onCreate() {
dbHelper = new DbHelper(getContext());
// TODO: Implement this to initialize your content provider on startup.
return true;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
return db.delete("Student", "number = ?", new String[]{uri.getPathSegments().get(1)});
}
@Override
public String getType(Uri uri) {
switch (uriMatcher.match(uri)) {
case STUDENT_DIR:
return "vnd.android.cursor.dir/vnd." + AUTHORITY + ".student";
case STUDENT_ITEM:
return "vnd.android.cursor.item/vnd." + AUTHORITY + ".student";
default:
break;
}
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
Long number = db.insert("Student", null, values);
Log.d("tag", "insert: " + number);
return Uri.parse("content://" + AUTHORITY + "/student/" + number);
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteDatabase db = dbHelper.getReadableDatabase();
return db.query("Student", projection, selection, selectionArgs, null, null, sortOrder);
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
return db.update("Student", values, "name = ?", new String[]{uri.getPathSegments().get(1)});
}
}
這里沿用數(shù)據(jù)存儲篇中的工程來展示效果塞俱，onClick中代碼更改如下
//搜索結(jié)果這里
case R.id.btn_search:
printTable();
setBlank();
break;
//-----------------------------------分界線------------------------------------//
private void printTable() {
StringBuilder stringBuilder = new StringBuilder();
// Cursor cursor = db.query("Student", null, null, null, null, null, null, null);
Uri uri = Uri.parse(contentUri);
Cursor cursor = getContentResolver().query(uri, null, null, null, null);
if (cursor.moveToFirst()) {
do {
String n = cursor.getString(cursor.getColumnIndex("name"));
String b = cursor.getString(cursor.getColumnIndex("number"));
stringBuilder.append("姓名：" + n + "，學(xué)號：" + b + "\n");
} while (cursor.moveToNext());
}
tvStudent.setText("學(xué)生數(shù)據(jù)：\n" + stringBuilder.toString());
cursor.close();
}
寫入
寫入三個數(shù)據(jù)吏垮，結(jié)果如圖所示
image.png
case R.id.btn_insert:
ContentValues cv = getContentValues();
// db.insert("Student", null, cv);
Uri uri = Uri.parse(contentUri);
getContentResolver().insert(uri, cv);
//清空Editext的輸入
setBlank();
break;
刪除
通過學(xué)號刪除xima這個學(xué)生
image.png
case R.id.btn_delete:
String number = etNumber.getText().toString();
if (!number.isEmpty()){
// db.delete("Student", "number = ?", new String[]{number});
Uri uriDelete = Uri.parse(contentUri + "/" + number);
getContentResolver().delete(uriDelete, null, null);
setBlank();
}
break;
更新
libai的學(xué)號更新到233
image.png
case R.id.btn_update:
String name = etName.getText().toString();
Uri uriUpdate = Uri.parse(contentUri + "/" + name);
if (!name.isEmpty())
getContentResolver().update(uriUpdate, getContentValues(), null, null);
// db.update("Student", getContentValues(), "name = ?", new String[]{name});
setBlank();
break;
最后
我覺得吧ContentProvider就跟數(shù)據(jù)庫差不多障涯，就調(diào)用的方式有所差別罐旗。
然后由于我在數(shù)據(jù)存儲篇偷懶只弄了一張表，這邊也只能是一張表唯蝶，因為跟書上的有所區(qū)別九秀，改了我好久，好慘啊...
偷懶需謹(jǐn)慎啊
