我正在尝试创建一个“待办事项列表”，除了保存数据外，我已经完成了所有工作。我很新，想知道是否有人可以告诉我如何在内部保存数据。
这是我的代码：
main_to do list.Java
public class Main_ToDoList extends Activity implements OnClickListener
{
private Button btnAdd;
private EditText et;
private ListView lv;
ArrayList<String> list = new ArrayList<String>();
ArrayAdapter<String> adapter;
final Context context = this;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
btnAdd = (Button)findViewById(R.id.addTaskBtn);
btnAdd.setOnClickListener(this);
et = (EditText)findViewById(R.id.editText);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, list);
// set the lv variable to your list in the xml
lv=(ListView)findViewById(R.id.list);
lv.setAdapter(adapter);
// set ListView item listener
lv.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
@Override
public void onItemClick(AdapterView<?> parent, View view, final int position, long id)
{
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(context);
alertDialogBuilder.setTitle("Confirm Delete");
alertDialogBuilder.setMessage("Sure you want to delete?");
alertDialogBuilder.setCancelable(false);
alertDialogBuilder.setPositiveButton("Yes", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialogInterface, int i)
{
adapter.remove(adapter.getItem(position));
}
});
alertDialogBuilder.setNegativeButton("No", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialogInterface, int i)
{
dialogInterface.cancel();
}
});
AlertDialog alertDialog = alertDialogBuilder.create();
alertDialog.show();
}
});
}
public void onClick(View v)
{
String input = et.getText().toString();
if(input.length() > 0)
{
adapter.add(input);
et.setText("");
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main__to_do_list, menu);
return true;
}
}
我如何保存我输入的数据？谢谢！
您有3种方法可以执行此操作：SharedPreferences文件数据库
如果你想存储大量数据而不是使用dataBase，如果你想存储让我们说10-30个任务你可以使用SharedPreferences，这是最快的方法。
在任何情况下，如果您熟悉写入/读取文件，它也将是一条好路径，但可能需要更多工作。
您可以创建一个DatabaseHandler类
package com.connection;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteStatement;
import android.util.Log;
public class DatabaseHandler extends SQLiteOpenHelper {
// ====================== String Variables ======================
// The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.example/databases/"; // Package name
private static final String DATABASE_NAME = "test"; // Database Name
// ++++++++++++++++++++++ int Variables ++++++++++++++++++++++
private static final int DATABASE_VERSION = 1; // Database Version
// = = = = = = = = = = = Other Variables = = = = = = = = = = ==
private SQLiteDatabase myDataBase;
private final Context myContext;
SQLiteDatabase db;
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.myContext = context;
}
public void db_open()
{
db = this.getWritableDatabase();
}
/**
* Creates a empty database on the system and rewrites it with your own
* database.
* */
public void createDataBase() throws IOException {
boolean dbExist = databaseExist();
if (dbExist) {
// do nothing - database already exist
} else {
// By calling this method and empty database will be created into
// the default system path
// of your application so we are gone a be able to overwrite that
// database with our database.
this.getReadableDatabase();
try {
copyDataBase(); // call method to copy database
db = this.getWritableDatabase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Mrthod to check database is exist or not
* @return
*/
public boolean databaseExist()
{
File dbFile = new File(DB_PATH + DATABASE_NAME);
return dbFile.exists();
}
/**
* Copies your database from your local assets-folder to the just created
* empty database in the system folder, from where it can be accessed and
* handled. This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException {
// Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DATABASE_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DATABASE_NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
/**
* Close Database
*/
@Override
public synchronized void close() {
if (myDataBase != null)
myDataBase.close();
super.close();
}
public void DB_close()
{
if(db!=null)
db.close();
}
/**
* Method to add data
*/
public boolean addData(int vno,String content1,String content2){
boolean status=false;
ContentValues values = new ContentValues();
String checkEntry = "select id from yourtable where id="+vno;// +"' AND userid="+userid;
Cursor magazinecursor = db.rawQuery(checkEntry, null);
if (magazinecursor.moveToFirst()) {
} else {
values.put("id", vno);
values.put("content1", content1);
values.put("content2", content2);
long check = db.insert("yourtable", null, values);
if (check > -1) {
Log.i("inserstatus", "yourtable insert successfull");
status = true;
} else {
Log.i("insertstatus", "yourtable insert unsuccessful");
}
}
return status;
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
然后在您要保存数据的Activity中
DatabaseHandler myDbHelper;
myDbHelper = new DatabaseHandler(MainActivity.this);
myDbHelper.db_open();
myDbHelper.addData(1,"sample",sample);
希望这会帮助你或其他....
我有一些类似的东西，我想存储少量数据，但不想使用内容提供商或文件所以我使用SharePreferences。 （ps我在键的末尾使用了随机数，只是为了使它唯一，但是用户稍后从列表中选择它，所以我知道了值）
SharedPreferences sp = this.getPreferences( Context.MODE_PRIVATE );
SharedPreferences.Editor editor = sp.edit();
Random rand = new Random();
int randomNum = rand.nextInt( 1000 );
editor.putString( "EQUATION_KEY_" + String.valueOf( randomNum ), textToSave);
editor.commit();