About MatrixCursor in Android

If you want to get a Cursor and no database returns a Cursor, you can use MatrixCursor to return a Cursor.

For more information, see the following section:
Assume that there is a database table structure as follows:

_ Id	Name	Price
R. drawable.Ic_launcher	Zhangsan	39
R. drawable.Ic_launcher	Lisi	40
R. drawable.Ic_launcher	Wangwu	41
R. drawable.Ic_launcher	Zhaoliu	42

Now let's use the MatrixCursor to create a table structure like above. The MatrixCursor can be fully understood through an example below !! (Original link: http://blog.csdn.net/yelangjueqi/article/details/21232659 welcome reprint, respect for others' labor results, reprint please indicate the source !!) The following is an example:

package com.test.matrixcursor;import android.app.ListActivity;import android.database.MatrixCursor;import android.os.Bundle;import android.support.v4.widget.SimpleCursorAdapter;import android.view.View;import android.widget.ListView;import android.widget.Toast;public class MainActivity extends ListActivity {     private static final String[] COLUMN_NAME = { "_id", "name", "price" };     private MatrixCursor matrixCursor;     @Override     protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);           createList();           //createList2();     }     private void createList() {          matrixCursor = new MatrixCursor(COLUMN_NAME, 1);          startManagingCursor(matrixCursor);          matrixCursor.addRow(new Object[] { R.drawable.ic_launcher, "zhangsan",                    39 });          matrixCursor                    .addRow(new Object[] { R.drawable.ic_launcher, "lisi", 40 });          matrixCursor                    .addRow(new Object[] { R.drawable.ic_launcher, "wangwu", 41 });          matrixCursor.addRow(new Object[] { R.drawable.ic_launcher, "zhaoliu",                    42 });          matrixCursor                    .addRow(new Object[] { R.drawable.ic_launcher, "sunqi", 43 });          setListAdapter(new SimpleCursorAdapter(this, R.layout.activity_main,                    matrixCursor, COLUMN_NAME, new int[] { R.id.icon, R.id.name,                              R.id.price }));     }     private void createList2() {          matrixCursor = new MatrixCursor(COLUMN_NAME, 1);          startManagingCursor(matrixCursor);          MatrixCursor.RowBuilder builder1 = matrixCursor.newRow();          builder1.add(R.drawable.ic_launcher);          builder1.add("zhangsan");          builder1.add(39);          MatrixCursor.RowBuilder builder2 = matrixCursor.newRow();          builder2.add(R.drawable.ic_launcher);          builder2.add("lisi");          builder2.add(40);          MatrixCursor.RowBuilder builder3 = matrixCursor.newRow();          builder3.add(R.drawable.ic_launcher);          builder3.add("wangwu");          builder3.add(41);          setListAdapter(new SimpleCursorAdapter(this, R.layout.activity_main,                    matrixCursor, COLUMN_NAME, new int[] { R.id.icon, R.id.name,                              R.id.price }));     }     @Override     protected void onListItemClick(ListView l, View v, int position, long id) {          super.onListItemClick(l, v, position, id);          matrixCursor.moveToPosition(position);          StringBuilder builder = new StringBuilder();          builder.append("Name:")                    .append(matrixCursor.getString(matrixCursor                              .getColumnIndex("name"))).append("\n");          builder.append("Price:")                    .append(matrixCursor.getString(matrixCursor                              .getColumnIndex("price"))).append("\n");          Toast.makeText(getApplicationContext(), builder.toString(), 1000)                    .show();     }}

The implementation steps only take three steps. The following describes the steps through character Arrays: Step 1. create a character array, and the value of the character array corresponds to the table field, as follows: String [] COLUMN_NAME = {"_ id", "name", "price "}; step 2. use the MatrixCursor construction method to construct a MatrixCursor. The input parameter is the field array created in step 1, as shown below: MatrixCursormatrixCursor = newMatrixCursor (COLUMN_NAME); you can also specify the initial size, such: matrixCursor = newMatrixCursor (COLUMN_NAME, 10 );
Step 3. adding a row of values through the addRow method of matrixCursor is equivalent to inserting a record into the database, as shown below: matrixCursor. addRow (new Object [] {R. drawable. ic_launcher, "zhangsan", 39 });
Note: Step 3 can also be achieved by constructing a MatrixCursor. RowBuilder, which is equivalent to inserting a record into the database, as shown below: MatrixCursor. RowBuilder builder1 = matrixCursor. newRow ();
Builder1.add (R. drawable. ic_launcher );
Builder1.add ("zhangsan ");
Builder1.add (39 );
// Builder1.add (399999); The MatrixCursor construction can be completed in the preceding three steps. The process of retrieving data from MatrixCursor is the same as that of Cursor!

Note: If the number of add objects in builder1 is greater than the number of fields, that is, builder1.add (399999) is enabled. Note that the following error is reported:
02-27 19:00:44. 882: W/dalvikvm (29036): threadid = 1: thread exiting with uncaught exception (group = 0x41e689a8)
02-27 19:00:44. 882: W/dalvikvm (29036): threadid = 1: uncaught exception occurred
02-27 19:00:44. 883: W/System. err (29036): java. lang. runtimeException: Unable to start activity ComponentInfo {com. test. matrixcursor/com. test. matrixcursor. mainActivity}: android. database. cursorIndexOutOfBoundsException: No more columns left.
02-27 19:00:44. 883: W/System. err (29036): at android. app. ActivityThread. initialize mlaunchactivity (ActivityThread. java: 2356)
02-27 19:00:44. 883: W/System. err (29036): at android. app. ActivityThread. handleLaunchActivity (ActivityThread. java: 2408)
02-27 19:00:44. 883: W/System. err (29036): at android. app. ActivityThread. access $600 (ActivityThread. java: 167)
02-27 19:00:44. 883: W/System. err (29036): at android. app. ActivityThread $ H. handleMessage (ActivityThread. java: 1378)
02-27 19:00:44. 883: W/System. err (29036): at android. OS. Handler. dispatchMessage (Handler. java: 107)
02-27 19:00:44. 883: W/System. err (29036): at android. OS. low.loop (low.java: 194)
02-27 19:00:44. 884: W/System. err (29036): at android. app. ActivityThread. main (ActivityThread. java: 5405)
02-27 19:00:44. 884: W/System. err (29036): at java. lang. reflect. Method. invokeNative (Native Method)
02-27 19:00:44. 884: W/System. err (29036): at java. lang. reflect. Method. invoke (Method. java: 525)
02-27 19:00:44. 884: W/System. err (29036): at com. android. internal. OS. ZygoteInit $ MethodAndArgsCaller. run (ZygoteInit. java: 838)
02-27 19:00:44. 884: W/System. err (29036): at com. android. internal. OS. ZygoteInit. main (ZygoteInit. java: 605)
02-27 19:00:44. 884: W/System. err (29036): at dalvik. system. NativeStart. main (Native Method)
02-27 19:00:44. 886: W/System. err (29036): Caused by: android. database. CursorIndexOutOfBoundsException: No more columns left.
02-27 19:00:44. 887: W/System. err (29036): at android. database. MatrixCursor $ RowBuilder. add (MatrixCursor. java: 206)
02-27 19:00:44. 887: W/System. err (29036): at com. test. matrixcursor. MainActivity. createList (MainActivity. java: 46)
02-27 19:00:44. 888: W/System. err (29036): at com. test. matrixcursor. MainActivity. onCreate (MainActivity. java: 20)
02-27 19:00:44. 889: W/System. err (29036): at android. app. Activity. Wait mcreate (Activity. java: 5127)
02-27 19:00:44. 889: W/System. err (29036): at android. app. Instrumentation. callActivityOnCreate (Instrumentation. java: 1151)
02-27 19:00:44. 890: W/System. err (29036): at android. app. ActivityThread. initialize mlaunchactivity (ActivityThread. java: 2320) running result: