android 数据库同步

package org.jerry;import org.hwq.dbutil.R;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.TextView;public class MainActivity extends Activity implements OnClickListener {private TextView info;private Button runWrongBtn;private Button runRightBtn;private Button showInfoBtn;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                holdUIComponents();        showInfo();    }private void holdUIComponents() {info = (TextView) findViewById(R.id.info);runWrongBtn = (Button) findViewById(R.id.runWrongBtn);runRightBtn = (Button) findViewById(R.id.runRightBtn);showInfoBtn = (Button) findViewById(R.id.showInfoBtn);runWrongBtn.setOnClickListener(this);runRightBtn.setOnClickListener(this);showInfoBtn.setOnClickListener(this);}public void onClick(View v) {switch (v.getId()) {case R.id.runWrongBtn:runWrong();break;case R.id.runRightBtn:runRight();break;case R.id.showInfoBtn:showInfo();break;}}private void runWrong() {//因为不同步，会导致异常：database is lockedRunWrongThread t0 = new RunWrongThread();RunWrongThread t1 = new RunWrongThread();t0.start();t1.start();try {t0.join();t1.join();} catch (InterruptedException e) {e.printStackTrace();}showInfo();}private void runRight() {//有同步，执行正常RunRightThread t0 = new RunRightThread();RunRightThread t1 = new RunRightThread();t0.start();t1.start();try {t0.join();t1.join();} catch (InterruptedException e) {e.printStackTrace();}showInfo();}private void showInfo() {int userNums = DBUtil.getUserNums(getApplicationContext());info.setText(Integer.toString(userNums));}class RunWrongThread extends Thread {@Overridepublic void run() {DBOpenHelper dbHelper = new DBOpenHelper(getApplicationContext());for (int i = 0; i < 100; i++) {User user = new User();user.setName("name" + i);user.setAge(i);user.setEmail("email" + i);dbHelper.insert(user);}dbHelper.close();}}class RunRightThread extends Thread {@Overridepublic void run() {for (int i = 0; i < 100; i++) {User user = new User();user.setName("name" + i);user.setAge(i);user.setEmail("email" + i);DBUtil.insertUser(getApplicationContext(), user);}DBUtil.close();}}}

package org.jerry;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBOpenHelper extends SQLiteOpenHelper{private static final String DB_NAME = "db";private static final int DB_VERSION = 1;private static final String T_USER = "t_user";private static final String T_USER_COLUMN_ID = "id";private static final String T_USER_COLUMN_NAME = "name";private static final String T_USER_COLUMN_AGE = "age";private static final String T_USER_COLUMN_EMAIL = "email";private static final String T_USER_SQL = "create table " + T_USER + " (" + T_USER_COLUMN_ID + " integer primary key autoincrement, " + T_USER_COLUMN_NAME + " text, " + T_USER_COLUMN_AGE + " integer, " + T_USER_COLUMN_EMAIL + " text)";public DBOpenHelper(Context context) {super(context, DB_NAME, null, DB_VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(T_USER_SQL);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}public void insert(User user) {if (user == null) {return;}final ContentValues values = new ContentValues();values.put(T_USER_COLUMN_NAME, user.getName());values.put(T_USER_COLUMN_AGE, user.getAge());values.put(T_USER_COLUMN_EMAIL, user.getEmail());final SQLiteDatabase db = getWritableDatabase();db.insert(T_USER, null, values);}public int getUserNums() {final SQLiteDatabase db = getReadableDatabase();final Cursor cursor = db.query(T_USER, null, null, null, null, null, null);if (cursor == null) {return 0;}int count = cursor.getCount();cursor.close();return count;}}

package org.jerry;import android.content.Context;public class DBUtil {private static DBOpenHelper dbHelper;private static void ensureDBHelperExist(Context context) {if (dbHelper == null) {dbHelper = new DBOpenHelper(context);}}/** * 插入user * @param context 务必使用ApplicationContext，直接使用activity/service的context可能导致内存泄露 * @param user */public synchronized static void insertUser(Context context, User user) {ensureDBHelperExist(context);dbHelper.insert(user);}/** * @param context 务必使用ApplicationContext，直接使用activity/service的context可能导致内存泄露 * @return */public synchronized static int getUserNums(Context context) {ensureDBHelperExist(context);return dbHelper.getUserNums();}public synchronized static void close() {if (dbHelper != null) {dbHelper.close();dbHelper = null;}}}

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