从微调器中获取条件，并根据条件从数据库中检索列表视图中的数据

1 回答

• 1

  以下是如何从两个微调器应用 SelectedItem 的工作示例，然后通过单击“搜索”按钮显示，仅列出包含两个项目的行（如果有） .

  这些示例基于您提供的方案 . 也就是说，有一个特定的城市和血型组列表可以通过Spinners选择 . 记录表包括两列以及两列 _id 和 name 的列 . 测试数据库中填充了100个随机名称，城市和血型 .

  布局 activity_main.xml

  <?xml version="1.0" encoding="utf-8"?>
  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:orientation="vertical"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:context=".MainActivity">
  
      <TextView
          android:id="@+id/title"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Blood Bank" />
  
      <Spinner
          android:id="@+id/select_bloodgroup"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content">
      </Spinner>
      <Spinner
          android:id="@+id/select_city"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content">
      </Spinner>
      <Button
          android:id="@+id/search"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Search"/>
      <ListView
          android:id="@+id/records_list"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content">
      </ListView>
  </LinearLayout>
  

  DatabaseHelper DBHelper.java

  public class DBHelper extends SQLiteOpenHelper {
  
      public static final String DBNAME = "bloodbank";
      public static final int DBVERSION = 1;
      public static final String TB_RECORDS = "records";
      public static final String COl_RECORDS_ID = BaseColumns._ID;
      public static final String COL_RECORDS_NAME = "_name";
      public static final String COL_RECORDS_BLOODGROUP = "_blood_group";
      public static final String COL_RECORDS_CITY = "_city";
  
      SQLiteDatabase mDB;
  
      public DBHelper(Context context) {
          super(context,DBNAME, null, DBVERSION);
          mDB = this.getWritableDatabase();
  
      }
  
      @Override
      public void onCreate(SQLiteDatabase db) {
          String crtrecords = "CREATE TABLE IF NOT EXISTS " +
                  TB_RECORDS + "(" +
                  COl_RECORDS_ID + " INTEGER PRIMARY KEY," +
                  COL_RECORDS_NAME + " TEXT," +
                  COL_RECORDS_CITY + " TEXT, " +
                  COL_RECORDS_BLOODGROUP + " TEXT" +
                  ")";
          db.execSQL(crtrecords);
      }
  
      @Override
      public void onUpgrade(SQLiteDatabase db, int i, int i1) {
  
      }
  
      public long addRecord(String name, String city, String bloodgroup) {
          ContentValues cv = new ContentValues();
          cv.put(COL_RECORDS_NAME,name);
          cv.put(COL_RECORDS_CITY,city);
          cv.put(COL_RECORDS_BLOODGROUP,bloodgroup);
          return mDB.insert(TB_RECORDS,null,cv);
      }
  
      public Cursor getrecords(String city, String bloodgroup) {
          ArrayList<String> baseargs = new ArrayList<>();
          String whereclause = null;
          if (city != null && city.length() > 0) {
              whereclause = COL_RECORDS_CITY + "=?";
              baseargs.add(city);
          }
          if (bloodgroup != null && bloodgroup.length() > 0) {
              if (whereclause != null && whereclause.length() > 0) {
                  whereclause = whereclause + " AND ";
              } else whereclause = "";
              whereclause = whereclause + COL_RECORDS_BLOODGROUP + "=?";
              baseargs.add(bloodgroup);
          }
          String[] whereargs = null;
          if (baseargs.size() > 0) {
              whereargs = new String[baseargs.size()];
              for (int i =0; i < baseargs.size();i++) {
                  whereargs[i] = baseargs.get(i);
              }
          }
          return mDB.query(TB_RECORDS,null,whereclause,whereargs,null,null,COL_RECORDS_NAME);
      }
  }
  

  调用活动 MainActivity.java ： -

  public class MainActivity extends AppCompatActivity {
  
      //Specific Blood groups
      public static final String[] BLOODGROUPS = new String[]{
              "A+","A-","B+","B-","0+","0-","AB+","AB-"
      };
  
      //Specific Cities
      public static final String[] CITIES = new String[]{
              "London","Paris","New York","Montreal","Gurgaon"
      };
  
      // Some names for auto generation of test data
      static final String[] peoples_names = new String[]{
              "Fred","Mary","Bert","Anne","James","Susan","Tom","Theresa",
              "Cherles","Corrine","David","Diana","Edward","Esmerelda",
              "George","Gorgina","Harrold","Heather"
  
      };
  
      TextView mTitle;
      Spinner mBloodGroups, mCities;
      Button mSearch;
      DBHelper mDBHlpr;
      ArrayAdapter<String> mCitiesAdapter, mBloodGroupsAdapater;
      ListView mRecordsList;
      SimpleCursorAdapter mSCA;
      String mCurrentCities = "", mCurrentBloodGroups = "";
      Cursor mCsr;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          mTitle = this.findViewById(R.id.title);
          mBloodGroups = this.findViewById(R.id.select_bloodgroup);
          mCities = this.findViewById(R.id.select_city);
          mSearch = this.findViewById(R.id.search);
          mRecordsList = this.findViewById(R.id.records_list);
          mCurrentCities = "";
          mCurrentBloodGroups = "";
  
          // Add some test data
          mDBHlpr = new DBHelper(this);
          if (DatabaseUtils.queryNumEntries(mDBHlpr.getWritableDatabase(),DBHelper.TB_RECORDS) < 1) {
              Random rnd = new Random();
              rnd.setSeed(System.currentTimeMillis());
              for (int i = 0; i < 100; i++) {
                  mDBHlpr.addRecord(
                          peoples_names[rnd.nextInt(peoples_names.length)],
                          CITIES[rnd.nextInt(CITIES.length)],
                          BLOODGROUPS[rnd.nextInt(BLOODGROUPS.length)]
                  );
              }
          }
  
          //Setup City Spinner
          mCitiesAdapter = new ArrayAdapter<>(this,android.R.layout.simple_dropdown_item_1line,CITIES);
          mCities.setAdapter(mCitiesAdapter);
          //Setup Bloodgroups Spinner
          mBloodGroupsAdapater = new ArrayAdapter<>(this,android.R.layout.simple_dropdown_item_1line,BLOODGROUPS);
          mBloodGroups.setAdapter(mBloodGroupsAdapater);
          // Add Search Buitton Click Listener
          mSearch.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View view) {
                  mCurrentCities = mCities.getSelectedItem().toString();
                  mCurrentBloodGroups = mBloodGroups.getSelectedItem().toString();
                  refreshList();
              }
          });
          // Initial List (All)
          refreshList();
  
      }
  
      //Setup or refresh the ListView
      private void refreshList() {
          // Grab the data
          mCsr = mDBHlpr.getrecords(mCurrentCities,mCurrentBloodGroups);
          // If first time then setup the Cursor Adapter
          if (mSCA == null) {
              mSCA = new SimpleCursorAdapter(this,
                      android.R.layout.simple_list_item_2,
                      mCsr,
                      new String[]{DBHelper.COL_RECORDS_NAME,DBHelper.COL_RECORDS_CITY},
                      new int[]{android.R.id.text1, android.R.id.text2},
                      0
              );
              mRecordsList.setAdapter(mSCA);
          }
          // If not first time then swap the cursor
          else {
              mSCA.swapCursor(mCsr);
          }
      }
  }
  

  结果

  最初显示以下内容（因为数据是随机生成的，它可能会有所不同，尽管会列出100个项目）： -

  

  选择City Gurgaon之后： - （注意结果可能会因随机数据而有所不同）： -

  

  选择血型A-： - 后（结果可能会有所不同）： -

  

  • 注意此示例有效，目的是您从提供的代码中学习并进行您的研究，如果您有后续问题，那么您应该将它们作为Stack Overflow上的单独且不同的问题提出 .

  回复于 2024-04-25T18:06:15+08:00