Databases
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PO
 

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  1. PO
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    <p>You should make a separate class in its own file. Make it public, so other classes can see it, and give it some creation parameters.</p> <p>Pass the calling Activity to the class, then you can use that value for calls like toast that require the current Activity.</p> <pre><code>public class Read_from_db extends AsyncTask &lt;String, Long, Void&gt; { private final ProgressDialog dialog = new ProgressDialog(Read.this); private Activity callingActivity; public Read_from_db(Activity activity) { callingActivity = activity; } // can use UI thread here protected void onPreExecute() { this.dialog.setMessage("Wait\nSome SLOW job is being done..."); this.dialog.show(); } @Override protected Void doInBackground(String... arg0) { // TODO Auto-generated method stub try { //txtMsg.append("\n"); // obtain a list of from DB String TABLE_NAME = "classicpoems__poet_header"; String COLUMN_ID = "_id"; // String _ID = "_id"; String COLUMN_NAME = "poet_name"; String COLUMN_CENTURY = "century_start"; String [] columns ={COLUMN_ID,COLUMN_NAME,COLUMN_CENTURY}; Cursor c = db.query(TABLE_NAME,columns,null, null, null, null, COLUMN_ID); SimpleCursorAdapter adapter = new SimpleCursorAdapter(Read.this, R.layout.list_item, c, new String[] {COLUMN_ID,COLUMN_NAME,COLUMN_CENTURY}, new int[] {R.id.list_item_text_id,R.id.list_item_text_main,R.id.list_item_text_sub}, 0); ListView list = (ListView) findViewById(R.id.list_poet_name); list.setAdapter(adapter); } catch (Exception e) { Toast.makeText(callingActivity, e.getMessage(), 1).show(); Log.i(TAG, e.getMessage()); } db.close(); return null; } // can use UI thread here protected void onPostExecute(final Void unused) { if (this.dialog.isShowing()) { this.dialog.dismiss(); } // cleaning-up, all done this.dialog.setMessage("Done"); } } </code></pre>
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    1. POConvert a pice of code to class
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    1. COThanks for your help..I used contractor and now I can use current activity...But I have two problem first `findViewById` is undefined and second If I want to change `String [] columns` from my activity how I can define it?Can I create a new method in doInBackground method?
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    2. COif you pass an activity to your class, you can use callingActivity.findViewById()
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    3. COYou can also add a String[] parameter to your creation of your class
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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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