一起学Android之ContentProvider

移动开发作者： 2024-08-24 14:50:01

本文主要讲解在Android开发中ContentProvider的常规用法，仅供学习分享使用，如有不足之处，还请指正。

1 // 查询用户定义字典并返回结果
2 mCursor = getContentResolver().query(
3     UserDictionary.Words.CONTENT_URI, 单词表的内容URI
4     mProjection,1)"> 查询的数据列名数组
5     mSelectionClause                    查询条件，可以为null
6     mSelectionArgs,1)"> 查询参数，可以为null
7     mSortOrder);                         返回数据对象的排序条件

1 content:user_dictionary/words

1 Uri singleUri = ContentUris.withAppendedId(UserDictionary.Words.CONTENT_URI,4);

请求读取Provider的访问权限。
定义查询Provider的代码。

 1   "projection" 定义每行返回的列名数组
 2 String[] mProjection =
 3 {
 4     UserDictionary.Words._ID,1)">  _ID column name
 5     UserDictionary.Words.WORD,1)">  word column name
 6     UserDictionary.Words.LOCALE   locale column name
 7 };
 8 
 9  定义查询条件
10 String mSelectionClause = null;
11 
12  定义查询条件参数
13 String[] mSelectionArgs = {""};

/*
 2  * 定义查询参数
 3  */
 4 String[] mSelectionArgs = {"" 5 
 6  获取界面输入的查询条件
 7 mSearchString = mSearchWord.getText().toString();
此处插入代码校验数据是否有效
10 如果条件为空，则查询所有
11 if (TextUtils.isEmpty(mSearchString)) {
12      如果查询条件为空，则返回所有内容
13     mSelectionClause = 14     mSelectionArgs[0] = ""15 } else {
16      构造查询条件，匹配用户输入的数据.
17     mSelectionClause = UserDictionary.Words.WORD + " = ?"18      查询参数.
19     mSelectionArgs[0] = mSearchString;
20 }
21 
22  对表进行查询并返回Cursor对象
23 mCursor =24     UserDictionary.Words.CONTENT_URI,1)"> URI
25     mProjection,1)"> 查询数据列
26     mSelectionClause                    查询条件
27     mSelectionArgs,1)"> 查询参数
28     mSortOrder);                        返回结果排序行
29 
30  如果出现查询异常，则返回空
31 if (null == mCursor) {
32     33      * 插入代码捕获异常
34      35      如果返回为空，则没有匹配的内容
36 } else if (mCursor.getCount() < 1) {
37     38      * 通知用户查询不成功. 但这不是必须的39 } 40      插入代码处理结果
41 }

SELECT _ID,word,locale FROM words WHERE word = <userinput> ORDER BY word ASC;

通过拼接用户输入和列名的方式构造查询条件
2 String mSelectionClause =  "var = " + mUserInput;

 用一个可替换参数来包含用户输入
2 String mSelectionClause =  "var = ?";

 定义一个查询条件的数组
2 String[] selectionArgs = {""};

 将用户数据作为参数数据
2 selectionArgs[0] = mUserInput;

 定义从Cursor中检索并加载到输出行的列名
 2 String[] mWordListColumns =
 4     UserDictionary.Words.WORD,1)"> word column name
 5     UserDictionary.Words.LOCALE   7 
 8 //定义一个视图ID列表，该列表将接收每行的Cursor列
int[] mWordListItems = { R.id.dictWord,R.id.locale};
10 
 创建一个SimpleCursorAdapter对象
12 mCursorAdapter = new SimpleCursorAdapter(
13     getApplicationContext(),1)"> 应用程序上下文对象
14     R.layout.wordlistrow,1)"> ListView单行配置文件 
15     mCursor,1)"> query函数返回的结果
16     mWordListColumns,1)"> Cursor中的列名数组
17     mWordListItems,1)"> ListView中Item项的布局文件
18     0);                                     Flags (usually none are needed)
19 
 设置 adapter到ListView
21 mWordList.setAdapter(mCursorAdapter);

 定义"word"列的索引
int index = mCursor.getColumnIndex(UserDictionary.Words.WORD);
 3 
 4  5  * 当cursor有效的时候才执行.  User Dictionary Provider如果发生内部错误，将返回null,其他provider可能会抛出异常
 6   8 if (mCursor !=  9          * 移动到cursor的下一行.在第一行移动之前,行指向是-1，如果试图去查询此位置上的内容，将会抛出一个异常
11      while (mCursor.moveToNext()) {
13         获取对应的列的值.
14         newWord = mCursor.getString(index);
15          插入代码处理获取的值.
16         ...
17          while 循环结束
18     }
19 } 20      展示错误和异常信息
21 }

<uses-permission android:name="android.permission.READ_USER_DICTIONARY">

 定义一个新的 Uri对象，接收插入新行放回的内容
Uri mNewUri;
 要插入的新值
 5 ContentValues mNewValues =  ContentValues();
 6 
 * 设置每列对应的值
 9  10 mNewValues.put(UserDictionary.Words.APP_ID,"example.user");
11 mNewValues.put(UserDictionary.Words.LOCALE,"en_US"12 mNewValues.put(UserDictionary.Words.WORD,"insert"13 mNewValues.put(UserDictionary.Words.FREQUENCY,"100"14 
15 mNewUri = getContentResolver().insert(
16     UserDictionary.Word.CONTENT_URI,1)"> 内容 URI
17     mNewValues                           插入的值
18 );

user_dictionary/words/<id_value>

 包含更新的内容的对象
 2 ContentValues mUpdateValues =  定义需要更新的查询条件
 5 String mSelectionClause = UserDictionary.Words.LOCALE +  "LIKE ?" 6 String[] mSelectionArgs = {"en_%" 定义更新行得到的行数
int mRowsUpdated = 0 * 设置更新的内容.
13  14 mUpdateValues.putNull(UserDictionary.Words.LOCALE);
15 
16 mRowsUpdated = getContentResolver().update(
17     UserDictionary.Words.CONTENT_URI,1)">18     mUpdateValues                        更新的内容
19     mSelectionClause                    查询条件
20     mSelectionArgs                       查询内容参数
21 );

 定义需要删除的条件
 2 String mSelectionClause = UserDictionary.Words.APP_ID + " LIKE ?" 3 String[] mSelectionArgs = {"user" 4 
定义删除掉行数
int mRowsDeleted = 0 删除匹配条件的内容
 9 mRowsDeleted = getContentResolver().delete(
10     UserDictionary.Words.CONTENT_URI,1)">  URI
11     mSelectionClause                     删除条件
12     mSelectionArgs                       删除参数
13 );

integer
long integer (long)
floating point
long floating point (double)

批量访问：可以在ContentProviderOperation中使用方法创建批量处理访问调用，然后用ContentResolver.applyBatch()应用它们。
异步查询：应该在单独的线程中进行查询，其中一种方法是使用CursorLoader对象。
通过intents访问数据：虽然不能直接向提供者发送intent，但可以向provider's application发送intent，而provider's application序通常是最适合修改provider数据的应用程序。

1 String[] mProjection =
2 3     UserDictionary.Words._ID,4     UserDictionary.Words.WORD,1)">5     UserDictionary.Words.LOCALE
6 };

通讯记录URI
 2     private String call_uri = "content://call_log/calls" 4     内容解析器
 5     private ContentResolver mResolver;
 7     列表
 8      ListView lvCall;
 9 
10     获取的通讯记录的列名
11     private String[] columns =  String[]{
            CallLog.Calls._ID,CallLog.Calls.CACHED_NAME,CallLog.Calls.NUMBER,CallLog.Calls.TYPE,CallLog.Calls.DATE,CallLog.Calls.DURATION
13     };
15     @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
19         初始化内容解析器
20         mResolver = getContentResolver();
21         lvCall = (ListView) this.findViewById(R.id.lv_call);
23 
24     /**
25      * 获取通讯记录事件
26      * @param v
27      28     public  bn_call(View v) {
29         List<Map<String,String>> list = new ArrayList<>();
30         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss"31         Cursor cursor = mResolver.query(Uri.parse(call_uri),columns,1)">null,1)">,CallLog.Calls.DEFAULT_SORT_ORDER);
32         以下是为了转换数据格式
33         if(cursor!=){
34              (cursor.moveToNext()){
35                 long dt=cursor.getLong(cursor.getColumnIndex("date"));
36                 Date callDate =  Date(dt);
37                 String callDateStr = sdf.format(callDate);
38                 String name=cursor.getString(cursor.getColumnIndex("name"39                 String number=cursor.getString(cursor.getColumnIndex("number"40                 String duration =cursor.getString(cursor.getColumnIndex("duration"))+"s"41                 Map<String,String> map=new HashMap<String,String>() ;
42                 map.put("name"43                 map.put("number"44                 map.put("date"45                 map.put("duration"46                 list.add(map);
47             }
48         }
49         将数据填充到Adapter
50         SimpleAdapter adapter=new SimpleAdapter(51                 new String[]{"name","number","date","duration"},1)">52                 new int[]{R.id.tv_name,R.id.tv_number,R.id.tv_time,R.id.tv_duration});
53 
54         /*SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,cursor,1)">55                 new String[]{"name","date"},1)">56                 new int[]{R.id.tv_name,R.id.tv_time},1)">57                 CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);58         绑定Adapter到ListView
59         lvCall.setAdapter(adapter);
60     }

private String sms_uri="content://sms" 2 
 3     private String[] columns=            Telephony.Sms._ID,Telephony.Sms.ADDRESS,Telephony.Sms.CREATOR,Telephony.Sms.BODY,Telephony.Sms.DATE,Telephony.Sms.PERSON,Telephony.Sms.STATUS,Telephony.Sms.DATE_SENT
 ListView lvMsg;
        setContentView(R.layout.activity_main2);
15         mResolver=getContentResolver();
16         lvMsg= (ListView) .findViewById(R.id.lv_sms);
17 18 
19      bn_sms(View view) {
20         List<Map<String,1)">21         SimpleDateFormat sdf = 22         Cursor cursor = mResolver.query(Uri.parse(sms_uri),Telephony.Sms.DEFAULT_SORT_ORDER);
23         if (cursor != 24              (cursor.moveToNext()) {
25                 Log.e("TAG","bn_sms: "+cursor.getColumnIndex("person")+"---"+ cursor.getColumnIndex("date")+"---"+cursor.getColumnIndex("creator")+"---"+cursor.getColumnIndex("address"26                 long dt = cursor.getLong(cursor.getColumnIndex("date"27                 Date callDate = 28                 String callDateStr =29                 String person = cursor.getString(cursor.getColumnIndex("address"30                 String creator = cursor.getString(cursor.getColumnIndex("creator"31                 String duration =cursor.getString(cursor.getColumnIndex("duration"))+"s";
32                 String body = cursor.getString(cursor.getColumnIndex("body"33                 Map<String,String> map = 34                 map.put("person"35                 map.put("creator"36                 map.put("date"37                 map.put("duration",duration);
38                 map.put("body"39 40 41 42         43         SimpleAdapter adapter = 44                 new String[]{"person","creator","body"45                 46 
47                 lvMsg.setAdapter(adapter);
49     }