作用：把一个App中的数据库通过Url的形式共享出来，供其他App使用。
首先在App1中创建一个数据库，用SQLiteOpenHelper
public class MyOpenHelper extends SQLiteOpenHelper {
public MyOpenHelper(Context context){
super(context,"Account.db",null,1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table info(_id integer primary key autoincrement, name varchar(20),money varchar(10))");
db.execSQL("insert into info(name, money) values(?,?)",new String[]{"张三","5000"});
ContentValues cv = new ContentValues();
cv.put("name","李四");
cv.put("money","6000");
db.insert("info",null,cv);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
创建数据库：
MyOpenHelper myOpenHelper = new MyOpenHelper(this); myOpenHelper.getReadableDatabase();
然后用过ContentProvider把数据库共享出来，首先看代码：
public class MyProvider extends ContentProvider {
//定义一个Uri路径匹配器 (匹配不成功的时候会返回一个NO_MATCH返回一个-1)
private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);
private static final int QUERYSUCESS = 0;
private static final int INSERTSUCESS = 1;
private static final int UPADTESUCESS = 2;
private static final int DELETESUCESS = 3;
//创建一个静态代码块，在这里添加Uri
static {
/**
* authority 注意：和清单文件里面定义的一样 com.coderwei.provider/query
*/
sURIMatcher.addURI("com.coderwei.provider","query",QUERYSUCESS );
sURIMatcher.addURI("com.coderwei.provider","insert",INSERTSUCESS );
sURIMatcher.addURI("com.coderwei.provider","update",UPADTESUCESS );
sURIMatcher.addURI("com.coderwei.provider","delete",DELETESUCESS );
}
private MyOpenHelper myOpenHelper;
@Override
public boolean onCreate() {
//初始化MyOpenHelper
myOpenHelper = new MyOpenHelper(getContext());
return false;
}
@Nullable
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
if (sURIMatcher.match(uri)==QUERYSUCESS){
//说明路径匹配成功
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
Cursor cursor = db.query("info",projection,selection,selectionArgs,null,null,sortOrder);
//db.close();
//这里不能关闭Cursor
return cursor;
}else {
throw new IllegalArgumentException("uri路径不匹配");
}
}
@Nullable
@Override
public String getType(Uri uri) {
return null;
}
@Nullable
@Override
public Uri insert(Uri uri, ContentValues values) {
if (sURIMatcher.match(uri)==INSERTSUCESS){
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
long insert = db.insert("info",null,values);
Uri uri1 = Uri.parse("com.coderwei.insert/"+insert);
//db.close();
return uri1;
}else {
throw new IllegalArgumentException("uri路径不匹配");
}
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
if (sURIMatcher.match(uri)==DELETESUCESS){
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
int delete = db.delete("info",selection,selectionArgs);
//db.close();
return delete;
}else {
throw new IllegalArgumentException("uri路径不匹配");
}
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
if (sURIMatcher.match(uri)== UPADTESUCESS){
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
int update = db.update("info",values,selection,selectionArgs);
//db.close();
return update;
}else {
throw new IllegalArgumentException("uri路径不匹配");
}
}
}
代码很长，但是很简单，主要把上面四个增删改查方法实现就行，上面的db.close()关闭的时候报错了，所以就注释掉了，关不关都可以。
Insert方法返回的是一个Url对象，直接自己写一个就行了。
记得在Manifest.xml中配置ContentProvider：
<provider
android:authorities="com.coderwei.provider"
android:exported="true"
android:name=".MyProvider">
</provider>
android:authorities 自己随便给一个字符串，
android:exported="true"一定要写上这句，这句话表示可以被另一个Application的组件启动，没写可能会报错。
sURIMatcher.addURI("com.coderwei.provider","query",QUERYSUCESS );中的com.coderwei.provider就是这个字符串。
然后就是来到App2了，先看代码：
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void click1(View v){
doQuery();
}
public void click2(View v){
doInsert();
}
public void click3(View v){
doDelete();
}
public void click4(View v){
doUpdate();
}
private void doQuery(){
Uri uri = Uri.parse("content://com.coderwei.provider/query");
Cursor cursor = getContentResolver().query(uri,new String[]{"name","money"},null,null,null);
if (cursor!=null){
while (cursor.moveToNext()){
String name = cursor.getString(0);
String money = cursor.getString(1);
System.out.println("name:"+name+" money: "+money);
}
}
}
private void doInsert(){
Uri uri = Uri.parse("content://com.coderwei.provider/insert");
ContentValues cv = new ContentValues();
cv.put("name","王五");
cv.put("money","800");
Uri uri1 = getContentResolver().insert(uri,cv);
System.out.println("插入uri1:"+uri1);
}
private void doDelete(){
Uri uri = Uri.parse("content://com.coderwei.provider/delete");
int delete = getContentResolver().delete(uri,"name=?",new String[]{"王五"});
System.out.print("刪除了： "+delete);
}
private void doUpdate(){
Uri uri = Uri.parse("content://com.coderwei.provider/update");
ContentValues cv = new ContentValues();
cv.put("money","9000");
int update = getContentResolver().update(uri,cv,"name=?",new String[]{"王五"});
System.out.println("更新了："+update);
}
}
里面就是四个增删改查方法，就Query稍微麻烦一点，查询的结果返回一个Cursor对象，然后把这个Cursor对象的内容取出来就行了，