android怎么从数据库读取一条数据赋值给字符串
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发布时间：2022-04-22 01:35
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时间：2023-09-16 22:17
DatabaseActivity.java
package com.poqop.database;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.widget.CursorAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
import com.poqop.R;
public class DatabasesActivity extends Activity {
public LayoutInflater m;
ListView listView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.maintable);
DBAdapter db = new DBAdapter(this);
try {
String destPath = "/data/data/" + getPackageName() +
"/databases";
File f = new File(destPath);
if (true) {//!f.exists()) {
f.mkdirs();
f.createNewFile();
//---copy the db from the assets folder into
// the databases folder---
CopyDB(getBaseContext().getAssets().open("mydb"),
new FileOutputStream(destPath + "/MyDB"));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
listView=(ListView)findViewById(R.id.show3);
db.open();
for(int a=1;a<=3;a++)
{
int rowID=a;
Cursor c = db.getTitle(rowID);
if (c.moveToFirst())
inflateList(c);
else
Toast.makeText(this, "No title found",
Toast.LENGTH_LONG).show();
}
db.close();
}
public void CopyDB(InputStream inputStream,
OutputStream outputStream) throws IOException {
//---copy 1K bytes at a time---
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) > 0) {
outputStream.write(buffer, 0, length);
}
inputStream.close();
outputStream.close();
}
public void inflateList(Cursor c)
{
// 填充SimpleCursorAdapter
SimpleCursorAdapter adapter = new SimpleCursorAdapter(
DatabasesActivity.this,
R.layout.line, c,
new String[] { "_id", "name","email" }
, new int[] {R.id.my_title, R.id.my_content,R.id.my_content2},
CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER); //③
// 显示数据
listView.setAdapter(adapter);
}
}
DBAdapter.java
package com.poqop.database;
import java.util.HashMap;
import com.poqop.R;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class DBAdapter
{
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_EMAIL = "email";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "MyDB";
private static final String DATABASE_TABLE = "contacts";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE =
"create table titles (_id integer primary key autoincrement, "
+ "isbn text not null, title text not null, "
+ "publisher text not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion
+ " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS titles");
onCreate(db);
}
}
//---打开数据库---
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---关闭数据库---
public void close()
{
DBHelper.close();
}
//---向数据库中插入一个标题---
public long insertTitle(String name, String email)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_EMAIL, email);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//---删除一个指定标题---
public boolean deleteTitle(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID +
"=" + rowId, null) > 0;
}
//---检索所有标题---
public Cursor getAllTitles()
{
return db.query(DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_NAME,
KEY_NAME},
null,
null,
null,
null,
null);
}
//---检索一个指定标题---
public Cursor getTitle(long rowId) throws SQLException
{
Cursor mCursor =
db.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_NAME,
KEY_EMAIL},
KEY_ROWID + "=" + rowId,
null,
null,
null,
null,
null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//---更新一个标题---
public boolean updateTitle(long rowId, String name,
String email)
{
ContentValues args = new ContentValues();
args.put(KEY_NAME, name);
args.put(KEY_EMAIL, email);
return db.update(DATABASE_TABLE, args,
KEY_ROWID + "=" + rowId, null) > 0;
}
}
maintable.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello" />
<TableLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#DEDCD2"
android:stretchColumns="*">
<TableRow
android:background="#DEDCD2"
android:layout_margin="0.5dip">
<TextView
android:text="CA"
android:textColor="#0000FF"
android:textSize="20dip"
android:textStyle="bold"
android:ellipsize="marquee" />
<TextView
android:text="Device"
android:textColor="#0000FF"
android:textSize="20dip"
android:textStyle="bold"
android:ellipsize="marquee" />
<TextView
android:text="FixPage"
android:gravity="center"
android:textColor="#0000FF"
android:textSize="20dip"
android:textStyle="bold"
android:ellipsize="marquee" />
</TableRow>
</TableLayout>
<ListView
android:id="@+id/show3"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:drawSelectorOnTop="false"
/>
</LinearLayout>
line..xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal" >
<EditText
android:id="@+id/my_title"
android:layout_width="47dp"
android:layout_height="wrap_content"
android:layout_weight="0.27" />
<EditText
android:id="@+id/my_content"
android:layout_width="182dp"
android:layout_height="wrap_content"
android:layout_weight="0.22" />
<EditText
android:id="@+id/my_content2"
android:layout_width="182dp"
android:layout_height="wrap_content"
android:layout_weight="0.45" />
</LinearLayout>追问这是你从网上抄来的还是个错的吧
