Android APP 开发技术阶段总结（三）

Android sqlite数据库的查询

sqlite数据库底层封装

public class MyOpenHelper extends SQLiteOpenHelper{

    private static final String name = "mydb.db"; //数据库名称

    private static final Integer version = 1;

    @Override
    public void onCreate(SQLiteDatabase db) {
        // 第一次安装或者打开这个apk，会建立这个表
        Log.d("msg","第一次调用sqLite，建立表person...");
        db.execSQL("CREATE TABLE IF NOT EXISTS user (id integer primary key autoincrement, username varchar(20) unique," +
                " password varchar(20), email varchar(30), phone varchar(15), organization varchar(45), nickname varchar(40),"+
                " permission varchar(20), remark varchar(40))");

        //添加一个管理员账号
        db.execSQL("insert into user (username,password,email,phone,organization,nickname,permission,remark) " +
                " values(?,?,?,?,?,?,?,?)",
                new Object[]{"admin","admin","[email protected]","13457478543","1","admin","3","remark"});
        //添加三个筛选测试用账户
        db.execSQL("insert into user (username,password,email,phone,organization,nickname,permission,remark) " +
                        " values(?,?,?,?,?,?,?,?)",
                new Object[]{"admin1","admin1","[email protected]","13457478541","3","admin1","1","remark"});
        db.execSQL("insert into user (username,password,email,phone,organization,nickname,permission,remark) " +
                        " values(?,?,?,?,?,?,?,?)",
                new Object[]{"admin2","admin2","[email protected]","13457478542","2","admin2","2","remark"});
        db.execSQL("insert into user (username,password,email,phone,organization,nickname,permission,remark) " +
                        " values(?,?,?,?,?,?,?,?)",
                new Object[]{"admin3","admin3","[email protected]","13457478543","1","admin3","3","remark"});
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    //	 *     数据库文件会存放在/data/data/<package name>/databases/目录下
    public MyOpenHelper(Context context) {
        super(context, name, null, version);
    }

    public MyOpenHelper(Context context, DatabaseErrorHandler errorHandler) {
        super(context, name, null, version, errorHandler);
    }

    @Override
    public void onOpen(SQLiteDatabase db) {
        super.onOpen(db);
    }

    /**
     * 判断某张表是否存在
     * @param tabName 表名
     * @return
     */
    public boolean tabIsExist(String tabName){
        boolean result = false;
        if(tabName == null){
            return false;
        }
        SQLiteDatabase db = null;
        Cursor cursor = null;
        try {
            db = this.getReadableDatabase();//此this是继承SQLiteOpenHelper类得到的
            cursor = db.rawQuery("select count(*) from sqlite_master where type =? and name =?;", new String[]{"table",tabName});
            if(cursor.moveToNext()){
                int count = cursor.getInt(0);
                if(count>0){
                    result = true;
                }
            }

        } catch (Exception e) {
            // TODO: handle exception
        }
        return result;
    }
}

如何使用

SQLiteDatabase db = mySQLiteDataBase.getWritableDatabase();
ContentValues data = new ContentValues();
data.put("department_name",departmentName);
data.put("parent_id",parent_id);
db.insert("department", "department_name", data);
Log.d("gwj","增加了" + departmentName +"部门");
db.close();

当然也可以再进行一层封装，实现一张表的增删查改操作。然后再往上才是业务逻辑。

图片自动滑动

使用滑动控件

<AdapterViewFlipper
    android:id="@+id/flipper"
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:flipInterval="5000"
    android:layout_alignParentTop="true"/>

定义自己的图片滑动adapter

public class FilpperAdapter extends BaseAdapter {
    private Context mContext = null;
    private int[] mImageIds = null;

    public FilpperAdapter(Context context, int[] imageIds) {
        this.mContext = context;
        this.mImageIds = imageIds;
    }

    @Override
    public int getCount() {
        return mImageIds.length;
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    // 该方法返回的View代表了每个列表项
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView = null;
        if(null == convertView) {
            // 创建一个ImageView
            imageView = new ImageView(mContext);
            // 设置ImageView的缩放类型
            imageView.setScaleType(ImageView.ScaleType.FIT_XY);
            // 为imageView设置布局参数
            imageView.setLayoutParams(new ViewGroup.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
            convertView = imageView;
        } else {
            imageView = (ImageView) convertView;
        }

        // 给ImageView设置图片资源
        imageView.setImageResource(mImageIds[position]);

        return imageView;
    }
}

如何使用

mFlipper = (AdapterViewFlipper)getActivity().findViewById(R.id.flipper);
FilpperAdapter adapter = new FilpperAdapter(getContext(), mImageIds);
mFlipper.setAdapter(adapter);
mFlipper.startFlipping();
mFlipper.setFlipInterval(2000);

树型控件实现

包括界面和数据库的实现，本文实现了一个简单的部门树。

每个条目长按弹出菜单（删除本节点，增加叶节点，更改节点信息）。
由于代码数量太多，所以放到资源下载中，下载地址可以在评论区看到。
树型控件在完成过程中参考了如下博客，也算是站在了巨人的肩膀上。
https://blog.csdn.net/hqocshheqing/article/details/52134964
https://blog.csdn.net/lmj623565791/article/details/40212367