移动开发课程-作业3

设计目标:

1、contentprovider是安卓四大组件之一，请使用其方法类进行数据获取；2、请自建一个provider，然后在另一个app中使用resolver调用这个provider。3、本次作业请启用新项目，理论上需要两个APP进行实验。

代码解析：

  建立ContentProvider类，重写方法：

public class StuDbCP extends ContentProvider {

        private static final UriMatcher URI_MATCHER = new UriMatcher(UriMatcher.NO_MATCH);  //创建该内容提供者的匹配器
        private static final String AUTHORITY = "cth.android.contentprovider.StuDbCP";   //定义授权信息，用于获取该内容提供者的标识
        private static final String PATH = "student";                       //路径，表示访问内容提供者的具体路径，一般用表明表示访问该数据库的具体哪张表
        private static final int STU = 1;    //设定标志位，STU表示单条信息
        private static final int STUS = 2;   //STUS表示多条信息
static{
        URI_MATCHER.addURI(AUTHORITY, PATH + "/#", STU);   //给匹配器加入匹配规则
        URI_MATCHER.addURI(AUTHORITY, PATH, STUS);
        }

        private MyDBhelper stuDbHepler = null;
        private SQLiteDatabase stuDb = null;
@Override
public boolean onCreate() {
        boolean flag = false;
        stuDbHepler = new MyDBhelper(getContext(),1);  //创建SQLiteOpenHelper对象，版本为1
        if(stuDb != null) flag = true;
        return flag;
        }

@Override
public Cursor query(Uri uri, String[] projection, String selection,
        String[] selectionArgs, String sortOrder) {
        int flag = URI_MATCHER.match(uri);    //匹配传入的Uri
        Cursor selectResult = null;
        SQLiteDatabase db = stuDbHepler.getReadableDatabase();
        String whereClause = null;
        switch(flag) {
        case STU:
        whereClause = "id = "+ ContentUris.parseId(uri);  //如果匹配第一种方式表示后面跟了id，所以要先提取id
        if(selection != null&& selection.equals("")) {
        whereClause += " and "+ selection;   //把id加到where条件子句（下面几种方法此步骤作用同理）
        }
        selectResult = db.query("student", projection, whereClause, selectionArgs, null, null, null);
        break;
        case STUS:
        selectResult = db.query("student", projection,selection,selectionArgs, null, null, null);
        }

        return selectResult;
        }

/*返回uri的路径扩展部分的信息，一般单个条目返回字段为vnd.android.cursor.item/对应的PATH 而多个条目的以vnd.android.cursor.dir/对应的PATH。*/
@Override
public String getType(Uri uri) {

        int flag = URI_MATCHER.match(uri);
        switch(flag) {
        case STU:
        return"vnd.android.cursor.item/student";

        case STUS:
        return "vnd.android.cursor.dir/students";
        }
        return null;
        }

@Override
public Uri insert(Uri uri, ContentValues values) {
        int flag = URI_MATCHER.match(uri);
        Uri resultUri = null;
        switch(flag) {
        case STUS :
        stuDb = stuDbHepler.getWritableDatabase();   //获取写数据库
        long id = stuDb.insert(PATH, null, values);   //插入数据
        resultUri = ContentUris.withAppendedId(uri, id);  //建立插入的数据的URI
        break;
        }

        return resultUri;
        }

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
        int flag = URI_MATCHER.match(uri);
        String whereClause = null;
        int rowCount = -1;
        SQLiteDatabase db = stuDbHepler.getWritableDatabase();
        switch(flag) {
        case STU:
        whereClause = "id = "+ ContentUris.parseId(uri);
        if(selection != null&& selection.equals("")) {
        whereClause += " and "+ selection ;
        }
        rowCount = db.delete("student", whereClause, selectionArgs);
        break;

        case STUS:
        rowCount = db.delete("student", selection, selectionArgs);


default: break;
        }
        return rowCount;
        }

@Override
public int update(Uri uri, ContentValues values, String selection,
        String[] selectionArgs) {
        int flag = URI_MATCHER.match(uri);
        int count = -1;
        SQLiteDatabase db = stuDbHepler.getWritableDatabase();
        String whereClause = null;
        switch(flag) {
        case STU:
        whereClause = "id = "+ ContentUris.parseId(uri);
        if(selection != null&& selection.equals("")) {
        whereClause += " and "+ selection ;
        }
        count = db.update("student", values, whereClause, selectionArgs);
        break;
        case STUS:
        count = db.update("student", values, selection, selectionArgs);
        break;
        }
        return count;
        }

        }
新建resolverlei，写入插入函数：

public void insertData() {
    ContentResolver cr = getContext().getContentResolver();
    Uri uri = Uri.parse("content://cth.android.contentprovider.StuDbCP/student");
    ContentValues values = new ContentValues();
    values.put("name", "李四");
    values.put("age", 18);
    Uri resultUri = cr.insert(uri, values);
    if(resultUri != null) {
        Log.i("cth",resultUri.toString());
    } else{
        Log.e("cth","插入失败");
    }
}

运行展示截图：

点击button插入数据：