学习笔记|AS 数据共享ContentProvider
ContentProvider
ContentProvider提供了更为高级的数据共享方法，应用程序可以指定需要共享的数据，而其他应用程序则可以在不知道数据来源，路径的情况下，对共享数据进行查询、添加，删除和更新等操作。
一定要！一定要！注册 ContentProvider，在AndroidManifest.xml中
调用者不能直接调用ContentProvider的接口函数，而需要使用ContentResolver对象，通过URI间接调用ContentProvider，调用关系如下图
ok！！！！话不多说，直接上图，请看！！！！！！→
这个界面没得问题撒，就不多说了（需要源码的评论）。
接下来看下活动工程：
其中MainActivity是活动工程，People是声明 CONTENT_URI 和构造 Uri，PeopleProvider 是继承 Content Provider。继承Content Provider后，共有六个函数需要重载，分别是delete（）、getType（）、insert（）、onCreate（）、query（）和updat（）。增删查改更新就不同说了，getType（）函数用来返回指定URI的MIME数据类型。
我们先来看下People里面的代码：
public class People {
public static final String MIME_DIR_PREFIX = "vnd.android.cursor.dir";//多条数据
public static final String MIME_ITEM_PREFIX = "vnd.android.cursor.item";//单条数据
public static final String MINE_ITEM = "vnd.example.a86181.people";
public static final String MINE_TYPE_SINGLE = MIME_ITEM_PREFIX + "/" + MINE_ITEM;
public static final String MINE_TYPE_MULTIPLE = MIME_DIR_PREFIX + "/" + MINE_ITEM;
public static final String AUTHORITY = "com.example.a86181.content.peopleProvider";//授权者名称
public static final String PATH_SINGLE = "people/#";//单条数据的数据路径
public static final String PATH_MULTIPLE = "people";//多条数据的数据路径
public static final String CONTENT_URI_STRING = "content://" + AUTHORITY + "/" + PATH_MULTIPLE;
public static final Uri CONTENT_URI = Uri.parse(CONTENT_URI_STRING);//正式声明
public static final String KEY_ID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_AGE = "age";
public static final String KEY_HEIGHT = "height";
}
代码里面都标注的比较清除，我就不做说明了，有不理解的可以评论我。
然后我们在来看PeopleProvider里的代码：
public class PeopleProvider extends ContentProvider {
//创建名为people的数据库
//创建名为peopleinfo的数据表
//版本号为1
private static final String DB_NAME = "people.db";
private static final String DB_TABLE = "peopleinfo";
private static final int DB_VERSION = 1;
private SQLiteDatabase db;
private DBOpenHelper dbOpenHelper;
private static final int MULTIPLE_PEOPLE = 1;
private static final int SINGLE_PEOPLE = 2;
private static final UriMatcher uriMatcher;
//声明UriMatcher的匹配方式和返回代码
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(People.AUTHORITY, People.PATH_MULTIPLE, MULTIPLE_PEOPLE);
uriMatcher.addURI(People.AUTHORITY, People.PATH_SINGLE, SINGLE_PEOPLE);
}
@Override
public String getType(Uri uri) {
switch (uriMatcher.match(uri)) {
case MULTIPLE_PEOPLE:
return People.MINE_TYPE_MULTIPLE;
case SINGLE_PEOPLE:
return People.MINE_TYPE_SINGLE;
default:
throw new IllegalArgumentException("Unkown uri:" + uri);
}
}
@Override
//删除操作
public int delete(Uri uri, String selection, String[] selectionArgs) {
int count = 0;
switch (uriMatcher.match(uri)) {
case MULTIPLE_PEOPLE:
//删除全部数据
count = db.delete(DB_TABLE, selection, selectionArgs);
break;
case SINGLE_PEOPLE:
//根据指定id删除相应的数据
String segment = uri.getPathSegments().get(1);
count = db.delete(DB_TABLE, People.KEY_ID + "=" + segment, selectionArgs);
break;
default:
throw new IllegalArgumentException("Unsupported URI:" + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
@Override
//添加操作
public Uri insert(Uri uri, ContentValues values) {
long id = db.insert(DB_TABLE, null, values);
if (id > 0) {
Uri newUri = ContentUris.withAppendedId(People.CONTENT_URI, id);
getContext().getContentResolver().notifyChange(newUri, null);
return newUri;
}
throw new SQLException("Failed to insert row into " + uri);
}
@Override
//初始化数据集和建立数据连接
public boolean onCreate() {
Context context = getContext();
dbOpenHelper = new DBOpenHelper(context, DB_NAME, null, DB_VERSION);
db = dbOpenHelper.getWritableDatabase();
if (db == null) return false;
else return true;
}
@Override
//查询操作
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
qb.setTables(DB_TABLE);
switch (uriMatcher.match(uri)) {
case SINGLE_PEOPLE:
//根据指定id查询相应数据
qb.appendWhere(People.KEY_ID + "=" + uri.getPathSegments().get(1));
break;
default:
break;
}
//查询全部
Cursor cursor = qb.query(db,projection,selection,selectionArgs,null,null,sortOrder);
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return cursor;
}
@Override
//更新操作
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
int count;
switch (uriMatcher.match(uri)) {
case MULTIPLE_PEOPLE:
//跟新全部
count = db.update(DB_TABLE, values, selection, selectionArgs);
break;
case SINGLE_PEOPLE:
//更新指定id的数据
String segment = uri.getPathSegments().get(1);
count = db.update(DB_TABLE, values, People.KEY_ID + "=" + segment, selectionArgs);
break;
default:
throw new IllegalArgumentException("Unknow URI:" + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
//创建数据库操作
private static class DBOpenHelper extends SQLiteOpenHelper {
public DBOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
private static final String DB_CREATE = "create table " + DB_TABLE + " (" + People.KEY_ID + " integer primary key autoincrement, " + People.KEY_NAME + " text not null, " + People.KEY_AGE + " integer," + People.KEY_HEIGHT + " float);";
@Override
public void onCreate(SQLiteDatabase _db) {
_db.execSQL(DB_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase _db, int _oldVersion, int _newVersion) {
onCreate(_db);
}
}
}
代码里写的都很清楚了，就不做说明了。
最后再来看MainActivity里的代码：
public class MainActivity extends AppCompatActivity {
private EditText nameText;
private EditText ageText;
private EditText heightText;
private EditText idEntry;
private TextView labelView;
private TextView displayView;
private ContentResolver resolver;
addButtonListener addButtonListener = new addButtonListener();
queryAllButtonListener queryAllButtonListener = new queryAllButtonListener();
clearButtonListener clearButtonListener = new clearButtonListener();
deleteAllButtonListener deleteAllButtonListener = new deleteAllButtonListener();
queryButtonListener queryButtonListener = new queryButtonListener();
deleteButtonListener deleteButtonListener = new deleteButtonListener();
updateButtonListener updateButtonListener = new updateButtonListener();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nameText = (EditText) findViewById(R.id.name);
ageText = (EditText) findViewById(R.id.age);
heightText = (EditText) findViewById(R.id.height);
idEntry = (EditText) findViewById(R.id.id_entry);
labelView = (TextView) findViewById(R.id.label);
displayView = (TextView) findViewById(R.id.display);
Button addButton = (Button) findViewById(R.id.add);
Button queryAllButton = (Button) findViewById(R.id.query_all);
Button clearButton = (Button) findViewById(R.id.clear);
Button deleteAllButton = (Button) findViewById(R.id.delete_all);
Button queryButton = (Button) findViewById(R.id.query);
Button deleteButton = (Button) findViewById(R.id.delete);
Button updateButton = (Button) findViewById(R.id.update);
addButton.setOnClickListener(addButtonListener);
queryAllButton.setOnClickListener(queryAllButtonListener);
clearButton.setOnClickListener(clearButtonListener);
deleteAllButton.setOnClickListener(deleteAllButtonListener);
queryButton.setOnClickListener(queryButtonListener);
deleteButton.setOnClickListener(deleteButtonListener);
updateButton.setOnClickListener(updateButtonListener);
resolver = this.getContentResolver();
}
private class addButtonListener implements View.OnClickListener {
@Override
public void onClick(View v) {
ContentValues values = new ContentValues();
values.put(People.KEY_NAME,nameText.getText().toString());
values.put(People.KEY_AGE,Integer.parseInt(ageText.getText().toString()));
values.put(People.KEY_HEIGHT, Float.parseFloat(heightText.getText().toString()));
Uri newUri = resolver.insert(People.CONTENT_URI, values);
labelView.setText("添加成功，URI:" + newUri);
}
}
;
private class queryAllButtonListener implements View.OnClickListener {
@Override
public void onClick(View v) {
Cursor cursor = resolver.query(People.CONTENT_URI, new String[]{People.KEY_ID, People.KEY_NAME, People.KEY_AGE, People.KEY_HEIGHT}, null, null, null);
if (cursor == null) {
labelView.setText("数据库中没有数据");
return;
}
labelView.setText("数据库：" + String.valueOf(cursor.getCount()) + "条记录");
String msg = "";
if (cursor.moveToFirst()) {
do {
msg += "ID：" + cursor.getInt(cursor.getColumnIndex(People.KEY_ID)) + "，";
msg += "姓名：" + cursor.getString(cursor.getColumnIndex(People.KEY_NAME)) + "，";
msg += "年龄：" + cursor.getInt(cursor.getColumnIndex(People.KEY_AGE)) + "， ";
msg += "身高：" + cursor.getFloat(cursor.getColumnIndex(People.KEY_HEIGHT)) + "\n";
} while (cursor.moveToNext());
}
displayView.setText(msg);
}
}
;
private class clearButtonListener implements View.OnClickListener {
@Override
public void onClick(View v) {
displayView.setText("");
}
}
;
private class deleteAllButtonListener implements View.OnClickListener {
@Override
public void onClick(View v) {
resolver.delete(People.CONTENT_URI, null, null);
String msg = "数据全部删除";
labelView.setText(msg);
}
}
;
private class queryButtonListener implements View.OnClickListener {
@Override
public void onClick(View v) {
Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + idEntry.getText().toString());
Cursor cursor = resolver.query(uri, new String[]{People.KEY_ID, People.KEY_NAME, People.KEY_AGE, People.KEY_HEIGHT}, null, null, null);
if (cursor == null) {
labelView.setText("数据库中没有数据");
return;
}
String msg = "";
if (cursor.moveToFirst()) {
msg += "ID：" + cursor.getInt(cursor.getColumnIndex(People.KEY_ID)) + "，";
msg += "姓名：" + cursor.getString(cursor.getColumnIndex(People.KEY_NAME)) + "，";
msg += "年龄：" + cursor.getInt(cursor.getColumnIndex(People.KEY_AGE)) + "， ";
msg += "身高：" + cursor.getFloat(cursor.getColumnIndex(People.KEY_HEIGHT)) + "\n";
}
labelView.setText("数据库：");
displayView.setText(msg);
}
}
;
private class deleteButtonListener implements View.OnClickListener {
@Override
public void onClick(View v) {
Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + idEntry.getText().toString());
int result = resolver.delete(uri, null, null);
String msg = "删除ID为" + idEntry.getText().toString() + "的数据" + (result > 0 ? "成功" : "失败");
labelView.setText(msg);
}
}
;
private class updateButtonListener implements View.OnClickListener {
@Override
public void onClick(View v) {
ContentValues values = new ContentValues();
values.put(People.KEY_NAME, nameText.getText().toString());
values.put(People.KEY_AGE, Integer.parseInt(ageText.getText().toString()));
values.put(People.KEY_HEIGHT, Float.parseFloat(heightText.getText().toString()));
Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + idEntry.getText().toString());
int result = resolver.update(uri, values, null, null);
String msg = "更新ID为" + idEntry.getText().toString() + "的数据" + (result > 0 ? "成功" : "失败");
labelView.setText(msg);
}
}
;
}
对应的增删查改等基本操作都在里面了。代码根据相应的英文也很容易理解，就不一 一说明了，有部分不理解的欢迎评论。
展示成果了！！！！！
说明一下清除数据指的是，把显示的数据弄成不显示，display空
后面的ID删除，ID查询，ID更新就不操作了。但是，是可以操作的，有需要的把代码考下来自己演示哦。
刚开始写，也不知道怎么把自己的想法表示出来，反正不懂就问。就这么简单！