我在这里编辑了我以前的帖子。（如何使用 Android SQLite 数据库）
在这篇文章中，我更改了“显示”按钮的代码。现在我正在尝试访问数据库。我添加了一个 ListView 并尝试在其中显示数据库的内容。但再次得到同样的错误。（“不幸的是，学习已停止。”）点击“显示”按钮。
这是完整的代码 -
package com.example.learn;
import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
public class MainActivity extends Activity {
Button b1, b2, b3;
EditText t1;
ListView lv1;
SQLiteDatabase db;
Cursor c;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1 = (Button) findViewById(R.id.button1);
b2 = (Button) findViewById(R.id.button2);
b3 = (Button) findViewById(R.id.button3);
t1 = (EditText) findViewById(R.id.editText1);
lv1 = (ListView) findViewById(R.id.listView1);
db = openOrCreateDatabase("MyDB", MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS Names(Name VARCHAR)");
b1.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
if (t1.getText().toString().equals("")) {
t1.setText("Enter Name");
}
else {
String input = t1.getText().toString();
db.execSQL("INSERT INTO Names VALUES(" + "'" + input + "'"
+ ")");
}
}
});
b2.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
c = db.rawQuery("SELECT * FROM Names", null);
int count = c.getCount();
String[] values = new String[count + 1];
int i = 0;
do {
values[i] = c.getString(c.getColumnIndex("Name"));
i++;
} while (c.moveToNext());
// Define a new Adapter
// First parameter - Context
// Second parameter - Layout for the row
// Third parameter - ID of the TextView to which the data is
// written
// Forth - the Array of data
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
getBaseContext(), android.R.layout.simple_list_item_1,
android.R.id.text1, values);
// Assign adapter to ListView
lv1.setAdapter(adapter);
}
});
b3.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
db.execSQL("DELETE FROM Names");
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
and this is activity_main.xml -
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<EditText
android:id="@+id/editText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:ems="10"
android:hint="Add" >
</EditText>
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/editText1"
android:layout_marginTop="18dp"
android:text="@string/add" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button1"
android:layout_alignBottom="@+id/button1"
android:layout_centerHorizontal="true"
android:text="@string/show" />
<Button
android:id="@+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button2"
android:layout_alignBottom="@+id/button2"
android:layout_alignParentRight="true"
android:text="@string/del" />
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_below="@+id/button1" >
</ListView>
</RelativeLayout>
我觉得有问题
do {
values[i] = c.getString(c.getColumnIndex("Name"));
i++;
}
while (c.moveToNext());
现在有什么问题？请帮忙。