Android应用开发-数据存储和界面展现(二)（重制版）

// 自定义类MyOpenHelper继承自SQLiteOpenHelper
MyOpenHelper oh = new MyOpenHelper(getContext(), "person.db", null, 1);
// 获得数据库对象,如果数据库不存在，先创建数据库，后获得;如果存在，则直接获得
SQLiteDatabase db = oh.getWritableDatabase();

public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    db.execSQL("create table person (_id integer primary key autoincrement, name char(10), phone char(20), money integer(20))");
}

　　insert into person (name, phone, money) values (‘张三‘, ‘159874611‘, 2000);

　　delete from person where name = ‘李四‘ and _id = 4;

　　update person set money = 6000 where name = ‘李四‘;

　　select name, phone from person where name = ‘张三‘;

db.execSQL("insert into person (name, phone, money) values (?, ?, ?);", new Object[]{"张三", 15987461, 75000});// 插入
Cursor cs = db.rawQuery("select _id, name, money from person where name = ?;", new String[]{"张三"});    　　　 // 查找

protected void setUp() throws Exception {
    super.setUp();
    // 获取虚拟上下文对象
    oh = new MyOpenHelper(getContext(), "people.db", null, 1);
}

// 把要插入的数据以键值对的形式封装至ContentValues对象
ContentValues cv = new ContentValues();
cv.put("name", "刘能");
cv.put("phone", 1651646);
cv.put("money", 3500);
long i = db.insert("person", null, cv);　　// 返回值是所插入行的主键，如果出错返回-1

int i = db.delete("person", "_id = ? and name = ?", new String[]{"1", "张三"});    // 返回值是删除的行数

ContentValues cv = new ContentValues();
cv.put("money", 25000);
int i = db.update("person", cv, "name = ?", new String[]{"赵四"});    // 返回值是所修改行的主键，如果出错返回-1

//arg2:要查询的字段
//arg3:查询条件
//arg4:填充查询条件的占位符
Cursor cs = db.query("person", new String[]{"name", "money"}, "name = ?", new String[]{"张三"}, null, null, null);
while(cs.moveToNext()){
    //获取指定列的索引值
    String name = cs.getString(cs.getColumnIndex("name"));
    String money = cs.getString(cs.getColumnIndex("money"));
    System.out.println(name + ";" + money);
}

try {
    //开启事务
    db.beginTransaction();
    ...........
    //设置事务执行成功
    db.setTransactionSuccessful();
} finally{
    //关闭事务
    //如果此时已经设置事务执行成功，则sql语句生效，否则不生效
    db.endTransaction();
}

Cursor cs = db.query("person", null, null, null, null, null, null);
while(cs.moveToNext()){
    String name = cs.getString(cs.getColumnIndex("name"));
    String phone = cs.getString(cs.getColumnIndex("phone"));
    String money = cs.getString(cs.getColumnIndex("money"));
    //把读到的数据封装至Person对象
    Person p = new Person(name, phone, money);
    //把person对象保存至集合中
    people.add(p);
}

LinearLayout ll = (LinearLayout) findViewById(R.id.ll);
 for(Person p : people){
     //创建TextView，每条数据用一个文本框显示
     TextView tv = new TextView(this);
     tv.setText(p.toString());
     //把文本框设置为ll的子节点
     ll.addView(tv);
 }

Cursor cs = db.query("person", null, null, null, null, null, null, "0, 10");

//系统调用此方法，用来获知模型层有多少条数据
public int getCount() {
    return people.size();
}

//系统调用此方法，获取要显示至ListView的View对象
//position:是return的View对象所对应的数据在集合中的位置
public View getView(int position, View convertView, ViewGroup parent) {
    System.out.println("getView方法调用" + position);
    TextView tv = new TextView(MainActivity.this);
    //拿到集合中的元素
    Person p = people.get(position);
    tv.setText(p.toString());
    //把TextView的对象返回出去，它会变成ListView的条目
    return tv;
}

AlertDialog.Builder builder = new Builder(this);

builder.setTitle("警告");
builder.setMessage("若练此功，必先自宫");

builder.setPositiveButton("现在自宫", new OnClickListener() {

    @Override
    public void onClick(DialogInterface dialog, int which) {
        // TODO Auto-generated method stub
        Toast.makeText(MainActivity.this, "恭喜你自宫成功，现在程序退出", 0).show();
    }
});

builder.setNegativeButton("下次再说", new OnClickListener() {

    @Override
    public void onClick(DialogInterface dialog, int which) {
        // TODO Auto-generated method stub
        Toast.makeText(MainActivity.this, "若不自宫，一定不成功", 0).show();
    }
});

AlertDialog ad = builder.create();
ad.show();

AlertDialog.Builder builder = new Builder(this);
builder.setTitle("选择你的性别");

final String[] items = new String[]{
        "男", 
        "女"
};
//-1表示默认谁也不选中
//点击侦听的导包要注意别导错
builder.setSingleChoiceItems(items, -1, new OnClickListener() {

    //dialog：触发这个方法的对话框
    //which：用户所选的条目的下标
    @Override
    public void onClick(DialogInterface dialog, int which) {
        Toast.makeText(MainActivity.this, "您选择了" + items[which], 0).show();
        //关闭对话框
        dialog.dismiss();
    }
});
//可以直接用构建器显示对话框
builder.show();

AlertDialog.Builder builder = new Builder(this);
builder.setTitle("请选择你觉得帅的人");

final String[] items = new String[]{
        "吴彦祖",
        "吴亦凡",
        "刘德华",
        "古天乐"
};
//默认只选中第一个条目
final boolean[] checkedItems = new boolean[]{
        true,
        false,
        false,
        false,
};
builder.setMultiChoiceItems(items, checkedItems, new OnMultiChoiceClickListener() {

    //which：用户点击条目的下标
    //isChecked：用于判断用户点击该条目是选中还是取消
    @Override
    public void onClick(DialogInterface dialog, int which, boolean isChecked) {
        checkedItems[which] = isChecked;
    }
});
//设置一个确定按钮
builder.setPositiveButton("确定", new OnClickListener() {

    @Override
    public void onClick(DialogInterface dialog, int which) {
        StringBuffer sb = new StringBuffer();
        for(int i = 0;i < items.length; i++){
            sb.append(checkedItems[i] ? items[i] + " " : "");
        }
        Toast.makeText(MainActivity.this, sb.toString(), 0).show();
    }
});
builder.show();