在App中创建自定义内容提供商： MProvider ，如下所示：
内容提供商类： BirthProvider
public class BirthProvider extends ContentProvider {
//Content Provider Details
static final String PROVIDER_NAME = "com.mprovider.BirthdayDude";
static final String URL = "content://" + PROVIDER_NAME + "/friends";
static final Uri CONTENT_URI = Uri.parse(URL);
// fields for the database
static final String ID = "id";
static final String NAME = "name";
static final String BIRTHDAY = "birthday";
// integer values used in content URI
static final int FRIENDS = 1;
static final int FRIENDS_ID = 2;
// maps content URI "patterns" to the integer values that were set above
static final UriMatcher uriMatcher;
//database
static final String DATABASE_NAME = "BirthdayReminder";
static final String TABLE_NAME = "birthTable";
static final int DATABASE_VERSION = 1;
static final String CREATE_TABLE =
" CREATE TABLE " + TABLE_NAME +
" (id INTEGER PRIMARY KEY AUTOINCREMENT, " +
" name TEXT NOT NULL, " +
" birthday TEXT NOT NULL);";
// projection map for a query
private static HashMap<String, String> BirthMap;
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(PROVIDER_NAME, "friends", FRIENDS);
uriMatcher.addURI(PROVIDER_NAME, "friends/#", FRIENDS_ID);
}
DBHelper dbHelper;
// database declarations
private SQLiteDatabase database;
@Override
public boolean onCreate() {
// TODO Auto-generated method stub
Context context = getContext();
dbHelper = new DBHelper(context);
// permissions to be writable
database = dbHelper.getWritableDatabase();
if (database == null)
return false;
else
return true;
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
// TODO Auto-generated method stub
SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
// the TABLE_NAME to query on
queryBuilder.setTables(TABLE_NAME);
switch (uriMatcher.match(uri)) {//doubtfull...
// maps all database column names
case FRIENDS:
queryBuilder.setProjectionMap(BirthMap);
break;
case FRIENDS_ID:
queryBuilder.appendWhere(ID + "=" + uri.getLastPathSegment());
break;
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
if (sortOrder == null || sortOrder == "") {
// No sorting-> sort on names by default
sortOrder = NAME;
}
Cursor cursor = queryBuilder.query(database, projection, selection,
selectionArgs, null, null, sortOrder);
/**
* register to watch a content URI for changes
*/
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return cursor;
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
// TODO Auto-generated method stub
switch (uriMatcher.match(uri)) {
// Get all friend-birthday records
case FRIENDS:
return "vnd.android.cursor.dir/vnd.example.friends";
// Get a particular friend
case FRIENDS_ID:
return "vnd.android.cursor.item/vnd.example.friends";
default:
throw new IllegalArgumentException("Unsupported URI: " + uri);
}
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
// TODO Auto-generated method stub
long row = database.insert(TABLE_NAME, "", values);
// If record is added successfully
if (row > 0) {
Uri newUri = ContentUris.withAppendedId(CONTENT_URI, row);
getContext().getContentResolver().notifyChange(newUri, null);
return newUri;
}
throw new SQLException("Fail to add a new record into " + uri);
}
@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
// TODO Auto-generated method stub
int count = 0;
switch (uriMatcher.match(uri)) {
case FRIENDS:
// delete all the records of the table
count = database.delete(TABLE_NAME, selection, selectionArgs);
break;
case FRIENDS_ID:
String id = uri.getLastPathSegment(); //gets the id
count = database.delete(TABLE_NAME, ID + " = " + id +
(!TextUtils.isEmpty(selection) ? " AND (" +
selection + ')' : ""), selectionArgs);
break;
default:
throw new IllegalArgumentException("Unsupported URI " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
// TODO Auto-generated method stub
int count = 0;
switch (uriMatcher.match(uri)) {
case FRIENDS:
count = database.update(TABLE_NAME, values, selection, selectionArgs);
break;
case FRIENDS_ID:
count = database.update(TABLE_NAME, values, ID +
" = " + uri.getLastPathSegment() +
(!TextUtils.isEmpty(selection) ? " AND (" +
selection + ')' : ""), selectionArgs);
break;
default:
throw new IllegalArgumentException("Unsupported URI " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
// class that creates and manages the provider's database
private static class DBHelper extends SQLiteOpenHelper {
public DBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL(CREATE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
Log.w(DBHelper.class.getName(),
"Upgrading database from version " + oldVersion + " to "
+ newVersion + ". Old data will be destroyed");
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
}
}
现在，在.java类中：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void deleteAllBirthdays(View view) {
// delete all the records and the table of the database provider
String URL = "content://com.mprovider.BirthdayDude/friends";
Uri friends = Uri.parse(URL);
int count = getContentResolver().delete(
friends, null, null);
String countNum = "Total " + count + " records are deleted.";
Toast.makeText(getBaseContext(),
countNum, Toast.LENGTH_LONG).show();
}
public void addBirthday(View view) {
// Add a new birthday record
ContentValues values = new ContentValues();
values.put(BirthProvider.NAME,
((EditText) findViewById(R.id.name)).getText().toString());
values.put(BirthProvider.BIRTHDAY,
((EditText) findViewById(R.id.birthday)).getText().toString());
Uri uri = getContentResolver().insert(
BirthProvider.CONTENT_URI, values);
Toast.makeText(getBaseContext(),
"==>" + uri.toString() + " inserted!", Toast.LENGTH_LONG).show();
}
public void showAllBirthdays(View view) {
// Show all the birthdays sorted by friend's name
String URL = "content://com.mprovider.BirthdayDude/friends";
Uri friends = Uri.parse(URL);
Cursor c = getContentResolver().query(friends, null, null, null, "name");
String result = "Results:";
if (!c.moveToFirst()) {
Toast.makeText(this, result + " no content yet!", Toast.LENGTH_LONG).show();
} else {
do {
result = result + "\n" + c.getString(c.getColumnIndex(BirthProvider.NAME)) +
" with id " + c.getString(c.getColumnIndex(BirthProvider.ID)) +
" has birthday: " + c.getString(c.getColumnIndex(BirthProvider.BIRTHDAY));
} while (c.moveToNext());
Toast.makeText(this, result, Toast.LENGTH_LONG).show();
}
}
}
这里是xml文件，从中调用java文件中的所有三个方法。
<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:paddingBottom="10dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="10dp"
tools:context=".MainActivity" >
<EditText
android:id="@+id/name"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="@string/name" />
<EditText
android:id="@+id/birthday"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/name"
android:layout_below="@+id/name"
android:ems="10"
android:hint="@string/birthday" />
<Button
android:id="@+id/btnAdd"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="addBirthday"
android:layout_alignLeft="@+id/birthday"
android:layout_below="@+id/birthday"
android:layout_marginTop="30dp"
android:text="@string/add" />
<Button
android:id="@+id/btnShow"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/btnAdd"
android:layout_below="@+id/btnAdd"
android:layout_marginTop="20dp"
android:onClick="showAllBirthdays"
android:text="@string/show" />
<Button
android:id="@+id/btnDelete"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/btnShow"
android:layout_alignLeft="@+id/btnShow"
android:layout_marginTop="20dp"
android:onClick="deleteAllBirthdays"
android:text="@string/delete" />
最后，清单中的提供程序的Declation如下：
Permissions：
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.READ_USER_DICTIONARY" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.READ_CONTACTS"></uses-permission>
<uses-permission android:name="android.permission.READ_CALL_LOG"></uses-permission>
<uses-permission android:name="android.permission.WRITE_CALL_LOG"></uses-permission>
提供者：
<permission android:name="com.mprovider.BirthdayDude.READ_DATABASE" android:protectionLevel="normal"/>
<provider android:authorities="com.mprovider.BirthdayDude"
android:enabled="true"
android:exported="true"
android:name="com.mprovider.BirthProvider"
android:protectionLevel="signature"
android:readPermission="com.mprovider.BirthdayDude.READ_DATABASE"/>
==＆GT;现在，我正在尝试从上面的应用程序获取数据到我的第二个应用程序，如下所示：
App：AccessContents 这是我的java文件：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
showAllBirthdays();
}
public void showAllBirthdays() {
// Show all the birthdays sorted by friend's name
String URL = "content://com.mprovider.BirthdayDude/friends";
Uri friends = Uri.parse(URL);
ContentProviderClient yourCR = getContentResolver().acquireContentProviderClient(friends);
Cursor c = getContentResolver().query(friends, null, null, null, "name");
String result = "Results:";
if (!c.moveToFirst()) {
Toast.makeText(this, result + " no content yet!", Toast.LENGTH_LONG).show();
} else {
do {
result = result + "\n" + c.getString(c.getColumnIndex("name")) +
" with id " + c.getString(c.getColumnIndex("id")) +
" has birthday: " + c.getString(c.getColumnIndex("birthday"));
} while (c.moveToNext());
Toast.makeText(this, result, Toast.LENGTH_LONG).show();
}
}
}
但是，问题是光标内部没有数据。 可能是什么问题？
，错误是：
Caused by: java.lang.SecurityException: Permission Denial: reading com.mprovider.BirthProvider uri content://com.mprovider.BirthdayDude/friends from pid=22395, uid=10118 requires com.mprovider.BirthdayDude.READ_DATABASE, or grantUriPermission()
感谢。