如何重用ListViews的方法？

时间：2011-05-06 17:16:26

标签： android class listview methods adapter

我在ListAC ListActivity中有几个方法需要重用，并希望放入单独的类中（如果可能的话）。我将有几十个ListView活动（ListActivities即：ListAD，ListTCDS，listSFAR等等）将调用这些方法，这些方法在此活动中完全相同，但是'Cursor databaseCursor'中的唯一更改（即。每个ListActivity的表名称）。我计划将这些类和相关的内容放入他们自己的应用程序包中（即：com.myCompany.myApp.AC）此外，这些活动是否需要为查询的'ORDER BY'提供多个courser（即：“...'列出'ASC | DESC”，“......'标题'ASC | DESC”等）。 B4调用游标，我也有检查ExternalStorageState的方法。我从LeffelMania（THNX！）获得了类，StorageStateChecker（见下文），用于重用ExternalStorageState，我仍想使用它 - 即使它没有在下面的代码中实现。我决定退后一步重新考虑这个问题（我搞砸了自己 - 大声笑），让你们和女孩们更容易通过代码阅读。

如您所见，这将导致设备上出现大量不必要的冗余和字节空间。我需要在设备上挤压每一个空间，因为这个应用程序将是这些设备用户的唯一目的（如果项目向前移动 - LOL）。

所以，我需要一种方法来通过通过单独的类调用这些方法来减少它，如果可能的话，我编写这些方法和我的适配器的方式。任何有关建议，方法，方法和代码的帮助对我学习Java / Android都非常有帮助和帮助。日Thnx !!

*此信息相关，并且仍在继续HERE和HERE。

更新：已完成的类位于REVISED块中。 Thnx对所有人都有帮助，现在我对课程有了更好的理解。方法用法。

ListAC活动：

public class ListAC extends ListActivity {
/**
 * -- Called when the activity is first created
 * ===================================================================
 */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.list_view2);

    activityTitle = (TextView) findViewById(R.id.titleBarTitle);
    activityTitle.setText("ADVISORY CIRCULATORS");

    storageState();
    searchList();
    nextActivity(); 
}

/**
 * -- Check to See if the SD Card is Mounted & Loads Default List Order
 * ======================================================================
 **/
private void storageState() {
    if (android.os.Environment.getExternalStorageState().equals(
            android.os.Environment.MEDIA_MOUNTED)) {

        orderASC_Label();// Loads the list

    } else if (android.os.Environment.getExternalStorageState().equals(
            android.os.Environment.MEDIA_UNMOUNTED)) {
        Alerts.sdCardMissing(this);
    }
}

/**
 * -- Default List Order (Ascending)
 * =====================================================================
 **/
public void orderASC_Label() {
    Cursor databaseCursor = db.rawQuery(
            "SELECT * FROM AC_list ORDER BY `label` ASC", null);

    Adapter_AC databaseListAdapter = new Adapter_AC(this,
            R.layout.list_item, databaseCursor, new String[] { "label",
                    "title", "description", "gotoURL" }, new int[] {
                    R.id.label, R.id.listTitle, R.id.caption, R.id.dummy });

    databaseListAdapter.notifyDataSetChanged();
    this.setListAdapter(databaseListAdapter);
}

/**
 * -- Starts the Next Activity
 * =====================================================================
 **/
public void nextActivity() {

    final ListView lv = getListView();
    lv.setTextFilterEnabled(true);
    lv.setClickable(true);

    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> a, View v, int pos, long id) {

            String url = "";
            TextView tv = (TextView) v.findViewById(R.id.dummy);
            url = (String) tv.getTag();

            String lbl = "";
            TextView tv2 = (TextView) v.findViewById(R.id.label);
            lbl = (String) tv2.getTag();

            Intent i = new Intent(List_AC.this, DocView.class);
            i.putExtra("url", url);
            i.putExtra("label", lbl);
            startActivity(i);
        }
    });
}

/**
 * -- Dispatched when the Menu-Key is presses
 * =====================================================================
 **/
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_MENU) {
        Intent i = new Intent(List_AC.this, DashBoard.class);
        startActivity(i);
    }
    return super.onKeyDown(keyCode, event);
}

/**
 * -- Local Variables
 * =====================================================================
 **/
protected TextView activityTitle;
boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
String extStorageDirectory = Environment.getExternalStorageDirectory()
        .toString();
File dbfile = new File(extStorageDirectory
        + "/XXX/xxx/dB/xxx.db");
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(dbfile, null);

/** ======================= END ==================================== **/
}

我的适配器（AdaperAC）：

public class AdapterAC extends SimpleCursorAdapter {


static Cursor dataCursor;
private LayoutInflater mInflater;

public Adapter_AC(Context context, int layout, Cursor dataCursor,
        String[] from, int[] to) {
    super(context, layout, dataCursor, from, to);
    this.dataCursor = dataCursor;
    mInflater = LayoutInflater.from(context);
}

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

    ViewHolder holder;

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.list_item, null);

        holder = new ViewHolder();
        holder.text1 = (TextView) convertView.findViewById(R.id.label);
        holder.text2 = (TextView) convertView.findViewById(R.id.listTitle);
        holder.text3 = (TextView) convertView.findViewById(R.id.caption);
        holder.text4 = (TextView) convertView.findViewById(R.id.dummy);

        holder.text4.setVisibility(View.GONE);

        convertView.setTag(holder);

    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    dataCursor.moveToPosition(position);

    int label_index = dataCursor.getColumnIndex("label");
    String label = dataCursor.getString(label_index);

    int title_index = dataCursor.getColumnIndex("title");
    String title = dataCursor.getString(title_index);

    int description_index = dataCursor.getColumnIndex("description");
    String description = dataCursor.getString(description_index);

    int goto_index = dataCursor.getColumnIndex("gotoURL");
    String gotoURL = dataCursor.getString(goto_index);

    holder.text1.setText(label);
    holder.text1.setTag(label);
    holder.text2.setText(title);
    holder.text3.setText(description);
    //holder.text4.setText(gotoURL);
    holder.text4.setTag(gotoURL);

    return convertView;
}

static class ViewHolder {
    TextView text1;
    TextView text2;
    TextView text3;
    TextView text4;
}

}

修改为：

public class QueryDisplay extends ListActivity {

protected TextView activityTitle;

boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;

String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
File dbfile = new File(extStorageDirectory + "/myComp/myApp/dB/myApp.db");
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(dbfile, null);

private static final String QUERY_KEY = "QUERY_KEY";

/**
 * -- Called when the activity is first created
 * ===================================================================
 */
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.list_view2);

    Bundle extras = getIntent().getExtras();

    String q = null;
    if (extras != null) {

        q = extras.getString(QUERY_KEY);
        Log.i("tag", "getting extras" + extras);
    }

    reloadQuery(q);
}

public void reloadQuery(String q) {

    Log.i("tag", "reloadQuery");

    if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {

        Cursor c = db.rawQuery(q, null);
        setListAdapter(new QueryAdapter(this, c));
        db.close();

    }else {
        Alerts.sdCardMissing(this);
    }
}

private class QueryAdapter extends CursorAdapter {

    public QueryAdapter(Context context, Cursor c) {
        super(context, c);
        LayoutInflater.from(context);
    }

    @Override
    public void bindView(View v, Context context, Cursor c) {

            int tvLabel = c.getColumnIndexOrThrow("label");
            String label = c.getString(tvLabel);
            TextView labelTxt = (TextView) v.findViewById(R.id.label);

            if (labelTxt != null) {
                labelTxt.setText("(" + label + ")");
            }

            int tvTitle = c.getColumnIndexOrThrow("title");
            String title = c.getString(tvTitle);
            TextView titleTxt = (TextView) v.findViewById(R.id.listTitle);

            if (titleTxt != null) {
                titleTxt.setText(title);
            }

            int tvDescription = c.getColumnIndexOrThrow("description");
            String description = c.getString(tvDescription);
            TextView descriptionTxt = (TextView) v.findViewById(R.id.caption);

            if (descriptionTxt != null) {
                descriptionTxt.setText(description);
            }

            int tvGoto= c.getColumnIndexOrThrow("gotoURL");
            String gotoURL = c.getString(tvGoto);
            TextView gotoTxt = (TextView) v.findViewById(R.id.dummy);

            if (gotoTxt != null) {
                gotoTxt.setText(gotoURL);
            }

            gotoTxt.setVisibility(View.GONE);
            v.setTag(tvGoto);
    }

    @Override
    public View newView(Context context, Cursor c, ViewGroup parent) {

        final View v = LayoutInflater.from(context).inflate(R.layout.list_item, parent, false);
        return v;
    }
}
}

......以及如何致电＆amp;注入查询：

OnClickListener myClickListener = new OnClickListener() {
    @Override
    public void onClick(View v) {
        if (v == myBtn) {

            String queryKey = "SELECT * FROM a_tablet ORDER BY `column` ASC";
            Intent i = new Intent(CurrentClass.this,QueryDisplay.class);
            i.putExtra("QUERY_KEY", queryKey);
            startActivity(i);
            }

2 个答案:

答案 0 :(得分：2)

为了给你的Cursor提供一堆不同的查询选项，你似乎正在做大量的额外工作。

为什么没有一个ListActivity，只有一个CursorAdapter，当你想要启动Activity时，只需将查询放在Intent中？

我将处理一个小代码示例并在编辑中将其发布到此处，但您似乎真的过度思考了这一点。您要做的就是在ListView中显示查询结果。唯一改变的是查询。重用其他一切。

代码示例：

public class QueryDisplay extends ListActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        Bundle extras = getIntent().getExtras();

        if (extras != null)
            reloadQuery(extras.getString(QUERY_KEY));

    }

    private void reloadQuery(query) {
        // Build your Cursor here.
        setAdapter(new QueryAdapter(this, cursor));
    }

    private class QueryAdapter extends CursorAdapter {

        @Override
        public void bindView(View view, Context context, Cursor cursor) {
            // Set up your view here
        }

        @Override
        public View newView(Context context, Cursor cursor, ViewGroup parent) {
            // Create your new view here
            final View view = LayoutInflator.from(context).inflate(R.layout.your_query_list_item_layout, parent, false); 
            return view;
        }
    }
}

这就是你应该需要的所有代码（加上自定义视图的填充和构建Cursor）。每当您需要更改查询时，您只需要调用reloadQuery(String query)即可设置。

答案 1 :(得分：1)

您的扩展SimpleCursorAdapter的代码是否有任何相似之处？关于获取外部存储状态等代码，您可以实现一个名为Utils的类，并使其中的方法保持静态。您很可能需要Context或Activity作为参数传递。

例如，这是我的外部存储状态检查程序。

public static final boolean isExternalStorageAvailable() {
    if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
        return true;
    } else {
        return false;
    }
}

我的网络状态检查器。

public static final boolean isPreferedNetworkAvailable(final Context context) {
    final ConnectivityManager connectivityManager = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
    final NetworkInfo networkInfo = connectivityManager.getNetworkInfo(connectivityManager.getNetworkPreference());
    return networkInfo.isAvailable();
}
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