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 locked
RunWrongThread 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 {

@Override
public 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 {

@Override
public 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);
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(T_USER_SQL);
}

@Override
public 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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