Android程式設計 - 列出已安裝的Apps Package名稱

以下程式碼會查詢已安裝的Apps，並將結果顯示在ListView元件：


        PackageManager pmPack;
        pmPack = getPackageManager();
        List packinfo = pmPack.getInstalledPackages(PackageManager.GET_ACTIVITIES);
        String[] pak = new String[packinfo.size()];
        for ( int i=0; i < packinfo.size(); i++) {
        PackageInfo p = (PackageInfo) packinfo.get(i);
        pak[i] = p.packageName;
        }
        ListView lv = (ListView) findViewById(R.id.listView1);
        ArrayAdapter lstadapter = new ArrayAdapter(
        MainActivity.this,
        android.R.layout.simple_list_item_1, pak);
        lv.setAdapter(lstadapter);

Android程式設計 - 使用ColorStateList

在Android中設定元件顏色值時，有些情況下並不是只有單一顏色，而要與元件狀態關聯；例如按鈕按下時與放開後要使用不同顏色，這種情況就需要使用ColorStateList。

首先定義顏色，例如res/drawable/tab_color.xml


<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <!-- When selected -->
    < tem android:state_selected="true"  android:color="#000000" />    

   <!-- When not selected -->
   <item android:state_selected="false" android:color="#CFCFCF" />
 
    <!-- When pressed -->
   <item android:state_pressed="true" android:color="#FF0000" />

</selector>

程式中可透過以下方式建立ColorStateList，再設定到元件上。


TextView tv = (TextView) tabWidget.getChildAt(i).findViewById(android.R.id.title);
try {
XmlResourceParser parser = getResources().getXml(R.drawable.tab_color);
ColorStateList colors;
colors = ColorStateList.createFromXml(getResources(), parser);
tv.setTextColor(colors);
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

Android程式設計 - 使用ExpandableList

ExpandableListView提供分組的項目清單介面，使用者可將每一組的清單內容展開或是折疊起來。

1.      首先要建立ExpandableListView所使用的版面，包括群組版面及群組的子版面。

<RelativeLayout

  xmlns:android="http://schemas.android.com/apk/res/android"

  android:layout_width="match_parent"

  android:layout_height="wrap_content" >

  <TextView

     android:id="@+id/text_college"

     ... />

</RelativeLayout>

child.xml

<RelativeLayout

  xmlns:android="http://schemas.android.com/apk/res/android"

  android:layout_width="match_parent"

  android:layout_height="wrap_content" >

  <ImageView

     android:id="@+id/image_go"

     ... />

  <TextView

     android:id="@+id/text_department"

     ... />

</RelativeLayout>

2.      建立ExpandableListView之資料轉接器

public class CollegeListAdapter extends BaseExpandableListAdapter {

  private Context context;     

  private ArrayList groups;

  private ArrayList> childs;

  public CollegeListAdapter(Context context, ArrayList groups, ArrayList> childs) {

     this.context = context;

     this.groups = groups;

     this.childs = childs;

  }

  public Object getChild(int groupPosition, int childPosition) {

     return childs.get(groupPosition).get(childPosition);

  }

  public long getChildId(int groupPosition, int childPosition) {

     return childPosition;

  }

  public View getChildView(int groupPosition, int childPosition,

       boolean isLastChild, View convertView, ViewGroup parent) {

     View childView;   

     @SuppressWarnings("unchecked")

     String department = childs.get(groupPosition).get(childPosition);

           LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

     //建立子清單元件, 並設置元件對應的內容

     childView = layoutInflater.inflate(R.layout.child, null);

           TextView dept_name = (TextView) childView.findViewById(R.id.text_department);

     dept_name.setText(department);

           ImageView imageView = (ImageView)childView.findViewById(R.id.image_go);

     imageView.setImageResource(R.drawable.ic_go);

     return childView; 

  }

  public int getChildrenCount(int groupPosition) {

     return childs.get(groupPosition).size();

  }

  public Object getGroup(int groupPosition) {

     return groups.get(groupPosition);

  }

  public int getGroupCount() {

     return groups.size();

  }

  public long getGroupId(int groupPosition) {

     return groupPosition;

  }

  public View getGroupView(int groupPosition, boolean isExpanded,

       View convertView, ViewGroup parent) {

     View groupView;   

     String college = groups.get(groupPosition);

           LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

     //建立群組元件,並設置元件對應的內容

     groupView = layoutInflater.inflate(R.layout.group, null);

           TextView college_name = (TextView)groupView.findViewById(R.id.text_college);

     college_name.setText(college);

     return groupView;

  }

  public boolean hasStableIds() {

     return false;

  }

  public boolean isChildSelectable(int groupPos, int childPos) {

     return false;      //如果想要子列表可被點選，要改為回傳true

  }

}

3. 建立ExpandableListView所要顯示資料串列。

  ArrayList group;                    //群組列表 

  ArrayList> child;        //子列表 

     ...

  private void initializeData(){ 

     group = new ArrayList(); 

     child = new ArrayList>();    

     addInfo("電資學院",
new String[]{"電子系","電機系","資訊系","電腦通訊系"}); 

     addInfo("工程學院",
new String[]{"機械系","自動化系","工管系"});

  } 

  private void addInfo(String g,String[] c){

     group.add(g); 

     ArrayList childitem = new ArrayList(); 

     for(int i=0;ilength;i++){ 

       childitem.add(c[i]); 

     } 

     child.add(childitem); 

  }   

4. 設定ExpandableListView資料轉接器

     expandablelist = (ExpandableListView) findViewById(R.id.expandableListView1);

     expandablelist.setAdapter(
new CollegeListAdapter(MainActivity.this, group, child));