Android04

学生管理系统界面的显示

findAll()查到所有学生数据;

cursor.getString(cursor.getColumnIndex(columnName));

2.显示是一个LinearLayout 数据太多了,用滚动布局 (只能有一个子控件) 竖向滚动布局<ScrollView ></ScrollView> 横向滚动布局<HorizontalScrollView ></HorizontalScrollView> <ScrollView android:layout_width="fill_parent" android:layout_height="fill_parent" > <LinearLayout android:id="@+id/ll_result" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > </LinearLayout> </ScrollView> 3.显示数据逻辑 > 1. 创建文本TextView 2. 内容是查出的学生信息 3. 得到要显示的LinearLayout,添加进文本 4.清除原来数据

LinearLayout.removeAllView();

listview引入

是系统给我们提供的一个可以显示很多个item的控件 这个控件合理的控制了界面的显示,即使有1000000万个item要显示他也能扛的住

MVC

M:model 数据模型 V:view 界面展现 C:controller 控制器

listview的使用

使用步骤

在布局xml文件声明listview控件在java代码找到listview控件,设置数据适配器setAapter();可以设置ListView条目的点击事件,listview.setOnItemClickListener(); 适配器的操作 写一个类,继承BaseAdapter

重写四个方法

getCount()确定listview里面有多少个条目

getView(int positon)返回某个位置要显示的view对象

positon是当前的位置,位置从0开始

converView表示的是复用的视图,用于优化ListView处理

学生管理系统的升级

<ListView android:id="@+id/lv" android:layout_width="fill_parent" android:layout_height="fill_parent" > </ListView> /** * 获取数据库的全部记录,刷新显示数据 */ private void refreshData() { final List<Student> students = dao.findAll(); // ll_result.removeAllViews();// 把原来的数据给清除 // for (Student student : students) { // TextView tv = new TextView(this); // tv.setText(student.toString()); // ll_result.addView(tv); // } lv.setAdapter(new BaseAdapter() { @Override public int getCount() {//获取一共有多少个条目 return students.size(); } @Override public View getView(int position, View convertView, ViewGroup parent) { LinearLayout ll = new LinearLayout(MainActivity.this); ll.setOrientation(LinearLayout.HORIZONTAL); ll.setGravity(Gravity.CENTER_VERTICAL); ImageView iv = new ImageView(MainActivity.this); String sex = students.get(position).getSex(); if("male".equals(sex)){ iv.setImageResource(R.drawable.nan); }else { iv.setImageResource(R.drawable.nv); } TextView tv = new TextView(MainActivity.this); tv.setText( students.get(position).getName()); ll.addView(iv, 30, 30); ll.addView(tv); return ll; }

listview的优化的原理

就是讲变成gc垃圾的Item,在放到最后使用

public View getView(int position, View convertView, ViewGroup parent)

listview的优化

view view = null; if(convertView == null){ view = new TextView(MainActivity.this); }else{ view = convertView; }

采用打气筒创建view对象

View view = null; if (convertView == null) { // 把一个布局xml文件转化成view对象 view = View.inflate(MainActivity.this, R.layout.item, null); } else { view = convertView; }

通知数据适配器刷新数据

/** * 获取数据库的全部记录,刷新显示数据 */ private void refreshData() { students = dao.findAll(); if (adapter == null) { adapter = new MyAdapter(); lv.setAdapter(adapter); }else{ //通知数据适配器更新数据,而不是new出来新的数据适配器 adapter.notifyDataSetChanged(); } }

常见对话框

确定取消对话框

public void click01(View view) { AlertDialog.Builder builder = new Builder(this); builder.setTitle("警告:"); builder.setMessage("若练此功,必先自宫,是否继续?"); builder.setPositiveButton("确定自宫", new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(MainActivity.this, "啊....", 0).show(); } }); builder.setNegativeButton("想想再说", new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(MainActivity.this, "如不自宫,一定不成功", 0).show(); } }); AlertDialog dialog = builder.create(); dialog.show(); }

单选对话框

public void click02(View view) { AlertDialog.Builder builder = new Builder(this); builder.setTitle("请选择您的性别:"); final String[] items = { "男", "女", "中性" }; builder.setSingleChoiceItems(items, -1, new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(MainActivity.this, "您的性别:" + items[which], 0) .show(); } }); builder.setNegativeButton("取消选择", null); builder.show(); }

多选对花框

public void click03(View view) { AlertDialog.Builder builder = new Builder(this); builder.setTitle("请选择您爱吃的水果"); final String[] items = new String[] { "黄瓜", "苹果", "香蕉", "菠萝菠萝蜜" }; final boolean[] checkedItems = new boolean[] { true, true, false, false }; builder.setMultiChoiceItems(items, checkedItems, new OnMultiChoiceClickListener() { @Override public void onClick(DialogInterface dialog, int which, boolean isChecked) { Toast.makeText(MainActivity.this, items[which] + isChecked, 0).show(); checkedItems[which] = isChecked; } }); builder.setNegativeButton("取消选择", null); builder.show(); }

进度对话框

public void click04(View view) { final ProgressDialog pd = new ProgressDialog(this); pd.setTitle("提醒"); pd.setMessage("正在加载数据...请稍后"); pd.show(); new Thread() { public void run() { try { Thread.sleep(30000); } catch (InterruptedException e) { e.printStackTrace(); } pd.dismiss(); }; }.start(); }

进度条对话框

public void click05(View view) { final ProgressDialog pd = new ProgressDialog(this); pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); pd.setMax(100); pd.setTitle("提醒"); pd.setMessage("正在加载数据...请稍后"); pd.show(); new Thread() { public void run() { for (int i = 0; i <= 100; i++) { try { Thread.sleep(300); } catch (InterruptedException e) { e.printStackTrace(); } pd.setProgress(i); } pd.dismiss(); }; }.start(); } }

删除学生信息的对话框

view.findViewById(R.id.iv_delete).setOnClickListener( new OnClickListener() { @Override public void onClick(View v) { AlertDialog.Builder builder = new Builder(MainActivity.this); builder.setTitle("提醒"); builder.setMessage("是否删除这条学生信息?"); builder.setPositiveButton("删除", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Student student = students.get(position); String name = student.getName(); // 从数据库删除数据. dao.delete(name); Toast.makeText(MainActivity.this, "数据被删除了", 0) .show(); // 更新ui界面. refreshData(); } }); builder.setNegativeButton("取消", null); builder.show(); } }); return view; }

快速拖动

android:fastScrollEnabled="true"

数据库的另外一种增删改查的方法

用API进行增删改查 1.增 ContentValues values = new ContentValues(); values.put(columnName, value); db.insert(tableName,null,values); 2.删 db.delete(tableName, "name=?", new String[]{value}); 3.改 ContentValues values = new ContentValues(); values.put(columnName, value); db.update(tableName, values, "name=?", new String[] { value }); 4.查 Cursor cursor = db.query(tableName, 需要查询的列, "name=?", new String[]{value},null,null, 排序);

数据库的事物

db.beginTransaction(); // 开启事务 try { // 模拟转账的操作 db.execSQL("update account set money=money-100 where name='zhangsan'"); s.endsWith("haha"); db.execSQL("update account set money=money+100 where name='lisi'"); db.setTransactionSuccessful();// 设置事务执行成功 } finally { db.endTransaction(); }

常见数据适配器-simple和arrayAdapter

simpleAdapter

<!--TextView不是LinearLayout--> <?xml version="1.0" encoding="utf-8"?> <TextView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:textSize="20sp" android:textColor="#66ff0000" android:layout_height="wrap_content" > </TextView> public class MainActivity extends Activity { private ListView lv; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); lv = (ListView) findViewById(R.id.lv); String[] objects = new String[]{"Animation","App","content","Media","NFC","OS"}; lv.setAdapter(new ArrayAdapter<String>(this, R.layout.item, objects)); } }

arrayAdapter

public class MainActivity extends Activity { private ListView lv; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); lv = (ListView) findViewById(R.id.lv); List<Map<String, Object>> data = new ArrayList<Map<String,Object>>(); Map<String, Object> map1 = new HashMap<String, Object>(); map1.put("icon", R.drawable.ic_menu_preferences); map1.put("name", "功能设置"); data.add(map1); Map<String, Object> map2 = new HashMap<String, Object>(); map2.put("icon", R.drawable.ic_menu_recent_history); map2.put("name", "时钟设置"); data.add(map2); Map<String, Object> map3 = new HashMap<String, Object>(); map3.put("icon", R.drawable.ic_menu_refresh); map3.put("name", "同步设置"); data.add(map3); Map<String, Object> map4 = new HashMap<String, Object>(); map4.put("icon", R.drawable.ic_menu_report_image); map4.put("name", "图片设置"); data.add(map4); lv.setAdapter(new SimpleAdapter(this, data, R.layout.item, new String[]{"icon","name"}, new int[]{R.id.iv,R.id.tv})); }

Android下的图形动画

log.xml

<?xml version="1.0" encoding="utf-8"?> <animation-list xmlns:android="http://schemas.android.com/apk/res/android" android:oneshot="false" > <item android:drawable="@drawable/logo1" android:duration="850"> </item> <item android:drawable="@drawable/logo2" android:duration="850"> </item> <item android:drawable="@drawable/logo3" android:duration="850"> </item> </animation-list>

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity" > <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/iv" /> </RelativeLayout> protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ImageView iv = (ImageView) findViewById(R.id.iv); iv.setBackgroundResource(R.drawable.logo); AnimationDrawable anim = (AnimationDrawable) iv.getBackground(); anim.start();//开始播放动画 }

应用程序的国际化

<?xml version="1.0" encoding="utf-8"?> <resources> <string name="app_name">13_i18n</string> <string name="action_settings">Settings</string> <string name="hello_world">hello world!</string> </resources> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hello_world" /> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/flag" /> </RelativeLayout>

样式和主题

<resources> <style name="text_content_style"> <item name="android:layout_width">match_parent</item> <item name="android:layout_height">wrap_content</item> <item name="android:textColor">#0000ff</item> <item name="android:textSize">20sp</item> </style> <style name="text_title_style" parent="@style/text_content_style"> <item name="android:textSize">25sp</item> </style> <style name="text_content_style.sub"> <item name="android:textSize">28sp</item> </style> </resources> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity" > <TextView style="@style/text_title_style" android:text="@string/hello_world" /> <TextView style="@style/text_content_style" android:text="@string/hello_world" /> <TextView style="@style/text_content_style.sub" android:text="@string/hello_world" /> <TextView style="@style/text_content_style" android:text="@string/hello_world" /> <TextView style="@style/text_content_style" android:text="@string/hello_world" /> <TextView style="@style/text_content_style" android:text="@string/hello_world" /> </LinearLayout>