MyDatabaseHelper.java 的内容如下：
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;
/**
* Created by toby on 17-12-28.
*/
public class MyDatabaseHelper extends SQLiteOpenHelper {
private static final String CREATE_BOOK = "create table Book (" +
"id integer primary key autoincrement, " +
"author text, " +
"price real, " +
"pages integer, " +
"name text)";
private static final String CREATE_CATEGORY = "create table Category (" +
"id integer primary key autoincrement, " +
"category_name text, " +
"category_code integer)";
private Context mContext;
public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory,
int version) {
super(context, name, factory, version);
mContext = context;
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
sqLiteDatabase.execSQL(CREATE_BOOK);
sqLiteDatabase.execSQL(CREATE_CATEGORY);
Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
switch (oldVersion) {
case 1:
sqLiteDatabase.execSQL(CREATE_CATEGORY);
// 不要加 break，以保证每次数据库的修改都会被执行
// break;
case 2:
sqLiteDatabase.execSQL("alter table Book add column category_id integer");
// 不要加 break，以保证每次数据库的修改都会被执行
// break;
default:
}
}
}
MyProvider.java 的代码如下：
import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
/**
* Created by toby on 18-1-2.
*/
public class MyProvider extends ContentProvider {
public static final int BOOK_DIR = 0;
public static final int BOOK_ITEM = 1;
public static final int CATEGORY_DIR = 2;
public static final int CATEGORY_ITEM = 3;
public static final String AUTHORITY = "com.syberos.learnandroid.provider";
private static UriMatcher uriMatcher;
private MyDatabaseHelper dbHelper;
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);
uriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);
uriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
uriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
}
@Override
public boolean onCreate() {
dbHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);
return true;
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] strings, @Nullable String s,
@Nullable String[] strings1, @Nullable String s1) {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = null;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
cursor = db.query("Book", strings, s, strings1, null, null, s1);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
cursor = db.query("Book", strings, "id = ?", new String[] { bookId },
null, null, s1);
break;
case CATEGORY_DIR:
cursor = db.query("Category", strings, s, strings1, null, null, s1);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
cursor = db.query("Category", strings, "id = ?", new String[] { categoryId },
null, null, s1);
break;
default:
break;
}
return cursor;
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
return "vdn.android.cursor.dir/"+AUTHORITY+".book";
case BOOK_ITEM:
return "vdn.android.cursor.item/"+AUTHORITY+".book";
case CATEGORY_DIR:
return "vdn.android.cursor.dir/"+AUTHORITY+".category";
case CATEGORY_ITEM:
return "vdn.android.cursor.item/"+AUTHORITY+".category";
default:
break;
}
return null;
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues contentValues) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
Uri uriReturn = null;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
case BOOK_ITEM:
long newBookId = db.insert("Book", null, contentValues);
uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + newBookId);
break;
case CATEGORY_DIR:
case CATEGORY_ITEM:
long newCategoryId = db.insert("Category", null, contentValues);
uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + newCategoryId);
break;
default:
break;
}
return uriReturn;
}
@Override
public int delete(@NonNull Uri uri, @Nullable String s, @Nullable String[] strings) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
int deleteRows = 0;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
deleteRows = db.delete("Book", s, strings);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
deleteRows = db.delete("Book", "id = ?", new String[] { bookId });
break;
case CATEGORY_DIR:
deleteRows = db.delete("Category", s, strings);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
deleteRows = db.delete("Category", "id = ?",
new String[] { categoryId });
break;
default:
break;
}
return deleteRows;
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues contentValues, @Nullable String s,
@Nullable String[] strings) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
int updateRows = 0;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
updateRows = db.update("Book", contentValues, s, strings);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
updateRows = db.update("Book", contentValues, "id = ?",
new String[] { bookId });
break;
case CATEGORY_DIR:
updateRows = db.update("Category", contentValues, s, strings);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
updateRows = db.update("Category", contentValues, "id = ?",
new String[] { categoryId });
break;
default:
break;
}
return updateRows;
}
}
使用的实例代码如下：
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
public class MainActivity extends Activity {
private static final String TAG = "MainActivity";
private MyDatabaseHelper dbHelper;
private String newId;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
}
@Override
protected void onDestroy() {
super.onDestroy();
}
public void create(View view) {
dbHelper.getWritableDatabase();
}
public void add(View view) {
Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book");
ContentValues values = new ContentValues();
values.put("name", "The first");
values.put("author", "None");
values.put("pages", 123);
values.put("price", 12.34);
Uri newUri = getContentResolver().insert(uri, values);
newId = newUri.getPathSegments().get(1);
}
public void update(View view) {
Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book/" + newId);
ContentValues values = new ContentValues();
values.put("price","10.00");
// 不指定，第三和第四个参数，将会更新所有行
getContentResolver().update(uri, values, "name = ?", new String[] {"The first"});
}
public void delete(View view) {
Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book/" + newId);
// 第二个和第三个参数如果不指定将会删除所有行
getContentResolver().delete(uri, "pages > ?", new String[] {"200"});
}
public void query(View view) {
Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book");
Cursor cursor = getContentResolver().query(uri, null, null,
null, null);
if (cursor != null && cursor.moveToFirst()) {
do {
String value = cursor.getString(cursor.getColumnIndex("name"));
Log.d(TAG, "Book name is " + value);
value = cursor.getString(cursor.getColumnIndex("author"));
Log.d(TAG, "Book author is " + value);
value = cursor.getString(cursor.getColumnIndex("pages"));
Log.d(TAG, "Book pages is " + value);
value = cursor.getString(cursor.getColumnIndex("price"));
Log.d(TAG, "Book price is " + value);
} while (cursor.moveToNext());
cursor.close();
}
}
public void replace(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.beginTransaction();
try {
db.delete("Book", null, null);
// if (true) { // 抛出一个异常测试事务
// throw new NullPointerException();
// }
ContentValues values = new ContentValues();
values.put("name", "The Third");
values.put("author", "Toby");
values.put("pages", 720);
values.put("price", 23.45);
db.insert("Book", null, values);
db.setTransactionSuccessful();
} catch (Exception e) {
e.printStackTrace();
} finally {
db.endTransaction();
}
}
}
布局文件的代码如下：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.syberos.learnandroid.MainActivity">
<Button
android:id="@+id/create"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="136dp"
android:layout_marginTop="22dp"
android:text="@string/create"
android:onClick="create"
/>
<Button
android:id="@+id/add"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/create"
android:layout_below="@+id/create"
android:layout_marginTop="17dp"
android:onClick="add"
android:text="@string/add"
/>
<Button
android:id="@+id/update"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/add"
android:layout_below="@+id/add"
android:layout_marginTop="11dp"
android:onClick="update"
android:text="@string/update" />
<Button
android:id="@+id/delete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/update"
android:layout_below="@+id/update"
android:layout_marginTop="15dp"
android:onClick="delete"
android:text="@string/delete" />
<Button
android:id="@+id/query"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/delete"
android:layout_below="@+id/delete"
android:layout_marginTop="14dp"
android:text="@string/query"
android:onClick="query"
/>
<Button
android:id="@+id/replace"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/query"
android:layout_below="@+id/query"
android:text="@string/replace"
android:onClick="replace"
/>
</RelativeLayout>
string 文件的内容如下：
<resources>
<string name="app_name">LearnAndroid</string>
<string name="create">create</string>
<string name="add">add</string>
<string name="update">update</string>
<string name="delete">delete</string>
<string name="query">query</string>
<string name="replace">replace</string>
</resources>
AndroidManifest.xml 的代码如下：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.syberos.learnandroid">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<provider
android:name="com.syberos.learnandroid.MyProvider"
android:authorities="com.syberos.learnandroid.provider"
android:exported="true" />
</application>
</manifest>
本文参考自 《Android 第一行代码》
