关于Android中使用Uri监听数据库的变化

网上原创的关于监听数据库变化的文章很少，基本没找到有用的一篇，所以自己去看了一下蓝牙传输的源码，写了一个Demo，放在这里给大家参考一下，看源码：

src里面有三个文件MyDataProvider、MainActivity和MyBean，看下面：

MyDataProvider.java:

public class MyDataProvider extends ContentProvider
{

// public static final String SCHEME = "test";
public static final String SCHEME = "content"; // 源码里面规定这样写，所以这个地方改变不了

public static final String HOST = "com.zyj";
public static final String PORT = "497393102";
public static final String PATH = "simple";

public static final int ALARMS = 1;
public static final String SHARE_LIST_TYPE = "com.zyj.test.dir/";
public static final int ALARMS_ID = 2;
public static final String SHARE_TYPE = "com.zyj.test.item/";

private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);

private SQLiteOpenHelper mDB = null;

// ===content://com.zyj:497393102/simple
public static final Uri CONTENT_URI = Uri.parse(SCHEME + "://" + HOST + ":" + PORT + "/" + PATH);

// 添加Uri的匹配方式，返回的就是上面自定义的整数类型，1代表操作的是一个批量，2操作的是单独的一个对象
static
{
sURIMatcher.addURI(HOST + ":" + PORT, PATH, ALARMS);
sURIMatcher.addURI(HOST + ":" + PORT, PATH + "/#", ALARMS_ID);
}

@Override
public boolean onCreate()
{
mDB = new MyDB(getContext()); // 获取数据库的引用
return mDB != null;
}

@Override
public String getType(Uri uri)
{
// 得到我们自定义的Uri的类型，看上面你自己的定义
int match = sURIMatcher.match(uri);
switch (match)
{
case ALARMS:
{
return SHARE_LIST_TYPE;
}
case ALARMS_ID:
{
return SHARE_TYPE;
}
default:
{
throw new IllegalArgumentException("Unknown URI: " + uri);
}
}
}

@Override
public Uri insert(Uri uri, ContentValues values)
{
// 首先是看Uri和我们自定义的是否匹配，，匹配则将数据属性插入到数据库中并同志更新
SQLiteDatabase db = mDB.getWritableDatabase();
if (sURIMatcher.match(uri) != ALARMS)
{
throw new IllegalArgumentException("Unknown/Invalid URI " + uri);
}

ContentValues filteredValues = new ContentValues();
filteredValues.put(MyDB.BEAN_ID, values.getAsInteger(MyDB.BEAN_ID));
filteredValues.put(MyDB.MESSAGE, values.getAsString(MyDB.MESSAGE));
filteredValues.put(MyDB.TASK_PROGRESS, values.getAsFloat(MyDB.TASK_PROGRESS));
long rowID = db.insert(MyDB.TABLET, null, filteredValues);
if (rowID != -1)
{
getContext().getContentResolver().notifyChange(uri, null);
}
return CONTENT_URI;
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs)
{

// 首先是看Uri和我们自定义的是否匹配，，匹配则进行删除

SQLiteDatabase db = mDB.getWritableDatabase();
int count = 0;
int match = sURIMatcher.match(uri);
switch (match)
{
case ALARMS:
case ALARMS_ID:
String where = null;
// 这里对selection进行匹配操作，看你传递的是一个批量还是一个单独的文件
if (selection != null)
{
if (match == ALARMS)
{
where = "( " + selection + " )";
}
else
{
where = "( " + selection + " ) AND ";
}
}
else
{
where = "";
}
if (match == ALARMS_ID)
{
// 如果你传递的是一个单独的文件，也就是Uri后面添加了/item的，那么在这里把该值与数据库中的属性段进行比较，返回sql语句中的where
String segment = uri.getPathSegments().get(1);
long rowId = Long.parseLong(segment);
where += " ( " + MyDB.BEAN_ID + " = " + rowId + " ) ";
}
count = db.delete(MyDB.TABLET, where, selectionArgs);
break;
default:
throw new UnsupportedOperationException("Cannot delete URI: " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}

@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)
{
// 基本同上了
SQLiteDatabase db = mDB.getWritableDatabase();

int count;
long rowId = 0;

int match = sURIMatcher.match(uri);
switch (match)
{
case ALARMS:
case ALARMS_ID:
{
String myWhere;
if (selection != null)
{
if (match == ALARMS)
{
myWhere = "( " + selection + " )";
}
else
{
myWhere = "( " + selection + " ) AND ";
}
}
else
{
myWhere = "";
}
if (match == ALARMS_ID)
{
String segment = uri.getPathSegments().get(1);
rowId = Long.parseLong(segment);
myWhere += " ( " + MyDB.BEAN_ID + " = " + rowId + " ) ";
}

if (values.size() > 0)
{
count = db.update(MyDB.TABLET, values, myWhere, selectionArgs);
}
else
{
count = 0;
}
break;
}
default:
{
throw new UnsupportedOperationException("Cannot update URI: " + uri);
}
}
getContext().getContentResolver().notifyChange(uri, null);

return count;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
{
SQLiteDatabase db = mDB.getReadableDatabase();
SQLiteQueryBuilder qb = new SQLiteQueryBuilder(); //SQLiteQueryBuilder是一个构造SQL查询语句的辅助类

int match = sURIMatcher.match(uri);
switch (match)
{
case ALARMS:
{
qb.setTables(MyDB.TABLET);
break;
}
case ALARMS_ID:
{
qb.setTables(MyDB.TABLET);
qb.appendWhere(MyDB.BEAN_ID + "=");
qb.appendWhere(uri.getPathSegments().get(1));
break;
}
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
Cursor ret = qb.query(db, projection, selection, selectionArgs, null, null, sortOrder);

if (ret != null)
{
ret.setNotificationUri(getContext().getContentResolver(), uri);
Log.d("zyj", "created cursor " + ret + " on behalf of ");
}
else
{
Log.d("zyj", "query failed in downloads database");
}
return ret;
}

private static class MyDB extends SQLiteOpenHelper
{

// 这里就是数据库了，数据库字段、名称、表名等...
private static final String DATABASE = "test_database";
public static final String TABLET = "test_table";
public static String ID = "_id";
public static String BEAN_ID = "_bean_id";
public static String MESSAGE = "_message";
public static String TASK_PROGRESS = "_progress";

private SQLiteDatabase mDB = null;

private final String msql = "CREATE TABLE IF NOT EXISTS " + TABLET + "( " + ID
+ " INTEGER PRIMARY KEY AUTOINCREMENT, " + BEAN_ID + " TEXT, " + MESSAGE + " TEXT, " + TASK_PROGRESS
+ " TEXT )";

private MyDB(Context context)
{
super(context, DATABASE, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db)
{
mDB = db;
mDB.execSQL(msql);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
// 升级，自己可以去实现
}
}
}

MyBean.java一个实例对象

public class MyBean
{

public int id = 0;

public String message = null;

public float progress = 0.0f;

public MyBean(int id)
{
this.id = id;
}

}

MainActivity.java主界面了

public class MainActivity extends Activity
{

TextView mMessage = null;

private ContentObserver mDatabaseListener = null;
private Handler mHand = null;

@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

mMessage = (TextView) findViewById(R.id.message);

init();

// 注册数据库的监听，对应的是特定的Uri
getContentResolver().registerContentObserver(MyDataProvider.CONTENT_URI, true, mDatabaseListener);
}

@Override
protected void onDestroy()
{
super.onDestroy();
// 注销掉监听
 getContentResolver().unregisterContentObserver(mDatabaseListener);
}

private void init()
{
mHand = new Handler();
// 数据库变动时的回调
 mDatabaseListener = new ContentObserver(mHand)
{
@Override
public boolean deliverSelfNotifications()
{
System.out.println("deliverSelfNotifications ---------------- ");
return super.deliverSelfNotifications();
}

@Override
public void onChange(boolean selfChange, Uri uri)
{
System.out.println("onChange ---------------- " + uri.toString());
super.onChange(selfChange, uri);
}

@Override
public void onChange(boolean selfChange)
{
System.out.println("onChange ---------------- ...");
super.onChange(selfChange);
}
};
}

private int count = 0;

public void onViewClick(View view)
{
switch (view.getId())
{
case R.id.add:
// 插入数据
 ContentValues calues = new ContentValues();
calues.put("_bean_id", count++);
calues.put("_message", "AAAAAAAAAAAAAAAAAAAAA");
calues.put("_progress", 0.0f);
getContentResolver().insert(MyDataProvider.CONTENT_URI, calues);
break;
case R.id.del:
// 如果找不到指定的_bean_id=1、2、3的，则数据库不进行增减，但还是会调用回调方法
getContentResolver().delete(Uri.parse(MyDataProvider.CONTENT_URI.toString() + "/1"), null, null);
getContentResolver().delete(Uri.parse(MyDataProvider.CONTENT_URI.toString() + "/2"), null, null);
getContentResolver().delete(Uri.parse(MyDataProvider.CONTENT_URI.toString() + "/3"), null, null);
break;
case R.id.modify:
ContentValues values = new ContentValues();
values.put("_message", "ZZZZZZZZZZZZZZZZZZZZZ");
// 这两中方法一样，这样就可以更加明白Uri中在后面添加的/item了数字的意思了
getContentResolver()
.update(Uri.parse(MyDataProvider.CONTENT_URI.toString() + "/5"), values, null, null);
getContentResolver().update(MyDataProvider.CONTENT_URI, values, "_bean_id=?", new String[] { "6" });
break;
case R.id.query:
showMessage(getContentResolver().query(MyDataProvider.CONTENT_URI, null, null, null, null));
break;
}
}

private void showMessage(Cursor c)
{
if (c == null)
{
return;
}
final StringBuffer sb = new StringBuffer();
if (c.getCount() > 0)
{
while (c.moveToNext())
{
MyBean bean = new MyBean(c.getInt(c.getColumnIndex("_bean_id")));
bean.message = c.getString(c.getColumnIndex("_message"));
bean.progress = c.getFloat(c.getColumnIndex("_progress"));
sb.append(bean.id + "\t\t\t:" + bean.message + "\t\t\t,progress = " + bean.progress + "\n");
}
}

c.close();

mHand.post(new Runnable()
{
public void run()
{
mMessage.setText(sb.toString());
}
});
}
}

activity_main.xml 上面就是四个按钮，下面就是一个TextView显示控件

<LinearLayout 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:orientation="vertical"
android:padding="10.0dip" >

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:orientation="vertical" >

<Button
android:id="@+id/add"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="onViewClick"
android:text="Add" />

<Button
android:id="@+id/del"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="onViewClick"
android:text="Delete" />

<Button
android:id="@+id/modify"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="onViewClick"
android:text="Modify" />

<Button
android:id="@+id/query"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="onViewClick"
android:text="Query" />
</LinearLayout>

<ScrollView
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:maxHeight="20dip" >

<TextView
android:id="@+id/message"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="20sp" />
</ScrollView>

</LinearLayout>

最后就是AndroidManifest.xml了，和平时一样的，只不过在里面将你自己定义的ContentProvider写上，类似我的这样：

<provider

android:name="com.example.databasetest.MyDataProvider"

android:authorities="com.zyj:497393102" />

上面的authorities属性是一定要写的，它就是上面MyDataProvider.java里面的CONTENT_URI的HOST + ":" + PORT，可以看下面画的，就比较清楚了。

content://com.example.project:200/folder/subfolder/etc

\---------/ \---------------------------/ \---/ \--------------------------/

scheme host port path

\--------------------------------/

authority

然后就没有了，可以自己运行，感受一下Uri和数据库的监听。

有错误之处希望能够之出来，谢谢！！！