GreenDao的使用與資料庫升級------完整解析版
阿新 • • 發佈：2019-02-16
#GreenDao的使用
一、在project build.grade中新增：
dependencies {
......
classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2'
}二、在app build.grade中新增：
...... apply plugin: 'org.greenrobot.greendao' android { ...... greendao { schemaVersion 1 //版本 daoPackage 'dao' // 一般為app包名+生成檔案的資料夾名 targetGenDir 'src/main/java' //生成檔案路徑 } } dependencies { ...... implementation 'org.greenrobot:greendao:3.2.2' implementation 'org.greenrobot:greendao-generator:3.2.2' }
三、建立Dao類（以下為示例）：
@Entity //必須新增
public class Student {
@Id //標誌為主鍵
private Long id;
private String name;
private String sex;
}四、建立好Dao類（其成員變數對應著表的各個屬性）後，點選build，對專案進行構建，這時將生成一個第二步驟路徑的dao資料夾：
dao資料夾中包含：
DaoMaster.class
DaoSession.class
StudentDao.class //由第三步驟中建立的Dao類決定五、建立Application的子類，實現整個程式生命週期Context的獲取：
public class MApplication extends Application {
private static Context mContext;
@Override
public void onCreate() {
super.onCreate();
mContext=this;
}
public static Context getContext() {
return mContext;
}
}六、在AndroidMainifest.xml中註冊MApplication:
<application
android:name=".MApplication"
......
</application>七、建立資料庫管理類、資料庫幫助類：
//資料庫幫助類
public class DatabaseHelper extends DaoMaster.OpenHelper {
public DatabaseHelper(Context context, String name) {
super(context, name);
}
@Override
public void onUpgrade(Database db, int oldVersion, int newVersion) {
MigrationHelper.getInstance().migrate(db, StudentDao.class);
}
}
//資料庫管理類
//這裡也可以學習一些單例模式的知識
public class DatabaseManager {
private static DatabaseManager databaseManager;
private static DatabaseHelper databaseHelper;
private static DaoMaster daoMaster;
private static DaoSession daoSession;
public static DatabaseManager getInstance() {
if(databaseManager==null) {
synchronized (DatabaseManager.class) {
if(databaseManager==null) {
databaseManager=new DatabaseManager();
}
}
}
return databaseManager;
}
public static DatabaseHelper getDatabaseHelper() {
if(databaseHelper==null) {
synchronized (DatabaseHelper.class) {
if(databaseHelper==null) {
databaseHelper=new DatabaseHelper(MApplication.getContext(),"Student.db");
}
}
}
return databaseHelper;
}
public static DaoMaster getDaoMaster() {
if(daoMaster==null) {
synchronized (DaoMaster.class) {
if(daoMaster==null) {
daoMaster=new DaoMaster(getDatabaseHelper().getWritableDatabase());
}
}
}
return daoMaster;
}
public static DaoSession getDaoSession() {
if(daoSession==null) {
synchronized (DaoSession.class) {
if(daoSession==null) {
daoSession=getDaoMaster().newSession();
}
}
}
return daoSession;
}
}八、完成activity_main.xml和MainActivity.java：
//activity_main.xml
<?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=".MainActivity">
<LinearLayout
android:id="@+id/ll_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="center"
android:layout_marginTop="20dp">
<TextView
android:id="@+id/tv_add"
android:layout_width="90dp"
android:layout_height="35dp"
android:text="Add"
android:textSize="20sp"
android:textStyle="bold"
android:gravity="center"
android:textColor="#FFFFFF"
android:background="@drawable/textview_shape"/>
<TextView
android:id="@+id/tv_display"
android:layout_width="90dp"
android:layout_height="35dp"
android:text="Show"
android:textSize="20sp"
android:textStyle="bold"
android:gravity="center"
android:textColor="#FFFFFF"
android:layout_marginLeft="30dp"
android:background="@drawable/textview_shape"/>
<TextView
android:id="@+id/tv_delete"
android:layout_width="90dp"
android:layout_height="35dp"
android:text="Delete"
android:textSize="20sp"
android:textStyle="bold"
android:gravity="center"
android:textColor="#FFFFFF"
android:layout_marginLeft="30dp"
android:background="@drawable/textview_shape"/>
</LinearLayout>
<ScrollView
android:layout_below="@+id/ll_button"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="15dp">
<TextView
android:id="@+id/tv_show"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"/>
</ScrollView>
</RelativeLayout>
//MainActivty.java
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private TextView addText,showText,deleteText,displayText;
private List<Student> studentList=new ArrayList<>();
private String text;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addText=(TextView)findViewById(R.id.tv_add);
deleteText=(TextView)findViewById(R.id.tv_delete);
showText=(TextView)findViewById(R.id.tv_show);
displayText=(TextView)findViewById(R.id.tv_display);
addText.setOnClickListener(this);
deleteText.setOnClickListener(this);
displayText.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.tv_add:
for(int i=1;i<=5;++i) {
DatabaseManager.getInstance().getDaoSession().insert(new Student(null,"student"+i,"男"));
}
break;
case R.id.tv_display:
text="";
studentList=DatabaseManager.getInstance().getDaoSession().getStudentDao().loadAll();
for(Student student : studentList) {
text=text+student.getId()+" "+student.getName()+" "+student.getSex()+"\n";
}
showText.setText(text);
break;
case R.id.tv_delete:
DatabaseManager.getInstance().getDaoSession().getStudentDao().deleteAll();
text="";
showText.setText(text);
break;
}
}
}以上步驟即可對GreenDao進行學習性使用
#GreenDao的資料庫升級
一、建立MigrationHelper類：
public class MigrationHelper {
private static final String CONVERSION_CLASS_NOT_FOUND_EXCEPTION = "MIGRATION HELPER - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS";
private static MigrationHelper instance;
public static MigrationHelper getInstance() {
if (instance == null) {
instance = new MigrationHelper();
}
return instance;
}
public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
generateTempTables(db, daoClasses);
DaoMaster.dropAllTables(db, true);
DaoMaster.createAllTables(db, false);
restoreData(db, daoClasses);
}
/**
* 生成臨時列表
*
* @param db
* @param daoClasses
*/
private void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
for (int i = 0; i < daoClasses.length; i++) {
DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
String divider = "";
String tableName = daoConfig.tablename;
String tempTableName = daoConfig.tablename.concat("_TEMP");
ArrayList<String> properties = new ArrayList<>();
StringBuilder createTableStringBuilder = new StringBuilder();
createTableStringBuilder.append("CREATE TABLE ").append(tempTableName).append(" (");
for (int j = 0; j < daoConfig.properties.length; j++) {
String columnName = daoConfig.properties[j].columnName;
if (getColumns(db, tableName).contains(columnName)) {
properties.add(columnName);
String type = null;
try {
type = getTypeByClass(daoConfig.properties[j].type);
} catch (Exception exception) {
exception.printStackTrace();
}
createTableStringBuilder.append(divider).append(columnName).append(" ").append(type);
if (daoConfig.properties[j].primaryKey) {
createTableStringBuilder.append(" PRIMARY KEY");
}
divider = ",";
}
}
createTableStringBuilder.append(");");
db.execSQL(createTableStringBuilder.toString());
StringBuilder insertTableStringBuilder = new StringBuilder();
insertTableStringBuilder.append("INSERT INTO ").append(tempTableName).append(" (");
insertTableStringBuilder.append(TextUtils.join(",", properties));
insertTableStringBuilder.append(") SELECT ");
insertTableStringBuilder.append(TextUtils.join(",", properties));
insertTableStringBuilder.append(" FROM ").append(tableName).append(";");
db.execSQL(insertTableStringBuilder.toString());
}
}
/**
* 儲存新的資料庫表 以及資料
*
* @param db
* @param daoClasses
*/
private void restoreData(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
for (int i = 0; i < daoClasses.length; i++) {
DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
String tableName = daoConfig.tablename;
String tempTableName = daoConfig.tablename.concat("_TEMP");
ArrayList<String> properties = new ArrayList();
for (int j = 0; j < daoConfig.properties.length; j++) {
String columnName = daoConfig.properties[j].columnName;
if (getColumns(db, tempTableName).contains(columnName)) {
properties.add(columnName);
}
}
StringBuilder insertTableStringBuilder = new StringBuilder();
insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
insertTableStringBuilder.append(TextUtils.join(",", properties));
insertTableStringBuilder.append(") SELECT ");
insertTableStringBuilder.append(TextUtils.join(",", properties));
insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");
StringBuilder dropTableStringBuilder = new StringBuilder();
dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);
db.execSQL(insertTableStringBuilder.toString());
db.execSQL(dropTableStringBuilder.toString());
}
}
private String getTypeByClass(Class<?> type) throws Exception {
if (type.equals(String.class)) {
return "TEXT";
}
if (type.equals(Long.class) || type.equals(Integer.class) || type.equals(long.class)) {
return "INTEGER";
}
if (type.equals(Boolean.class)) {
return "BOOLEAN";
}
Exception exception = new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));
exception.printStackTrace();
throw exception;
}
private List<String> getColumns(Database db, String tableName) {
List<String> columns = new ArrayList<>();
Cursor cursor = null;
try {
cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 1", null);
if (cursor != null) {
columns = new ArrayList<>(Arrays.asList(cursor.getColumnNames()));
}
} catch (Exception e) {
Log.v(tableName, e.getMessage(), e);
e.printStackTrace();
} finally {
if (cursor != null)
cursor.close();
}
return columns;
}
}二、編寫資料庫幫助類DatabaseHelper的onUpgrade方法 ：
public class DatabaseHelper extends DaoMaster.OpenHelper {
......
@Override
public void onUpgrade(Database db, int oldVersion, int newVersion) {
MigrationHelper.getInstance().migrate(db, StudentDao.class);
}
}三、任意修改Dao類或新增新的Dao類
四、在app build.gradle中增加資料庫版本號，然後對專案進行build，即可實現對資料庫的升級：
android {
......
greendao {
schemaVersion 2 //版本號+1
......
}
}