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我已经使用 DBhelper 在 android 中制作了一个简单的数据库应用程序，我已经放置了 2 个 Edittexts 和 2 个按钮，现在我想要的是当我按下“保存”时，2 个 edittexts 的值应该保存在数据库中。我尝试了以下代码，但它不是工作，请帮助我，在此先感谢。

主.java

       package com.example.db;

import android.os.Bundle;
import android.app.Activity;
import android.app.Dialog;
import android.content.Intent;
import android.graphics.Color;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
EditText e1,e2;
Button b1,b2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    e1=(EditText)findViewById(R.id.editText1);
    e2=(EditText)findViewById(R.id.editText2);
    b1=(Button)findViewById(R.id.button1);
    b2=(Button)findViewById(R.id.button2);
    final String fname = null;
    final String lname = null;

    b1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
             String f=e1.getText().toString();
                String l =e2.getText().toString();
                if(checkForNotEmpty(f, l)){
                try{
                    dbclas entry =new dbclas(MainActivity.this);
                entry.open();
                entry.createEntry(f,l);
                entry.close();
                }catch (Exception e) {
                    // TODO: handle exception
                    showMyDialog("Error", e.toString());
                }

            }
        Toast.makeText(getApplicationContext(),"Saved", 0).show();  
        }
    });
    b2.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Intent i =new Intent(MainActivity.this,Sqlview.class);
            startActivity(i);

        }
    });

    }
    private boolean checkForNotEmpty(String fname,String lname) {
        // TODO Auto-generated method stub

        if(fname.equals("")){
            showMyDialog("Error !!","Name Can't be blank");
            return false;
        }else if(lname.equals("")){
            showMyDialog("Error !!","Skill Can't be blank");
            return false;
        }else{
            return true;
        }
    }
    public void showMyDialog(String dialogType,String msg){
        Dialog da=new Dialog(this);
        da.setTitle(dialogType);
        TextView tv=new TextView(this);
        tv.setText(msg);
        if(dialogType.equals("Error !!")){
            tv.setTextColor(Color.RED);
        }else{
            tv.setTextColor(Color.YELLOW);
        }
        da.setContentView(tv);
        da.show();
    }

}

dbhelper.java

   package com.example.db;

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;

public class dbclas {

    public static final String KEY_ROWID="_id";
    public static final String FIRST_NAME="first_name";
    public static final String LAST_NAME="last_name";

    private static final String DATABASE_NAME="person";
    private static final String DATABASE_TABLE="persons_table";
    private static final int DATABASE_VERSION=1;

    private DBHelper myHelper;
    private final Context myContext;
    private SQLiteDatabase myDatabase;

    private static class DBHelper extends SQLiteOpenHelper{

        public DBHelper(Context context) {
            super(context,DATABASE_NAME,null,DATABASE_VERSION);
        // TODO Auto-generated constructor stub
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            // TODO Auto-generated method stub
            String query="CREATE TABLE "+DATABASE_TABLE+" ( "+KEY_ROWID+" INTEGER PRIMARY KEY, "+FIRST_NAME+" TEXT NOT NULL, "+LAST_NAME+" TEXT NOT NULL);";
            db.execSQL(query);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            // TODO Auto-generated method stub
            db.execSQL("DROP TABLE IF EXISTS"+DATABASE_TABLE);
            onCreate(db);
        }

    }
    public dbclas(Context c){
        myContext=c;
    }
    public dbclas open() throws SQLException{
        myHelper=new DBHelper(myContext);
        myDatabase=myHelper.getWritableDatabase();
        return this;
    }
    public void close(){
        myHelper.close();
    }
    public long createEntry(String fname, String lname) {
        // TODO Auto-generated method stub
        ContentValues cv=new ContentValues();
        cv.put(FIRST_NAME, fname);
        cv.put(LAST_NAME,lname);
        return myDatabase.insert(DATABASE_TABLE, null,cv);
    }
    public String getData() {
        // TODO Auto-generated method stub
        String[] columns=new String[]{KEY_ROWID,FIRST_NAME,LAST_NAME};
        Cursor c=myDatabase.query(DATABASE_TABLE, columns,null, null, null,null,null);
        String result="";
        int iRow=c.getColumnIndex(KEY_ROWID);
        int iName=c.getColumnIndex(FIRST_NAME);
        int iSkill=c.getColumnIndex(LAST_NAME);

        for(c.moveToFirst();!c.isAfterLast();c.moveToNext()){
            result=result+c.getString(iRow)+" "+c.getString(iName)+" "+c.getString(iSkill)+"\n";
        }
        return result;
    }
    public String getFName(Long l) {
        // TODO Auto-generated method stub
        String[] columns=new String[]{KEY_ROWID,FIRST_NAME,LAST_NAME};
        Cursor c=myDatabase.query(DATABASE_TABLE, columns, KEY_ROWID+"="+l, null, null, null, null);
        if(c!=null){
            c.moveToFirst();
            String name=c.getString(1);
            return name;
        }
        return null;
    }
    public String getLName(Long l) {
        // TODO Auto-generated method stub
        String[] columns=new String[]{KEY_ROWID,FIRST_NAME,LAST_NAME};
        Cursor c=myDatabase.query(DATABASE_TABLE, columns, KEY_ROWID+"="+l, null, null, null, null);
        if(c!=null){
            c.moveToFirst();
            String skill=c.getString(2);
            return skill;
        }
        return null;
    }
    public void updateEntry(long lRow, String mName, String mSkill) {
        // TODO Auto-generated method stub
        Log.v("in update method","...");
        ContentValues cvUpdate=new ContentValues();
        cvUpdate.put(FIRST_NAME, mName);
        cvUpdate.put(LAST_NAME,mSkill);
        myDatabase.update(DATABASE_TABLE, cvUpdate, KEY_ROWID+"="+lRow,null);

    }
    public boolean checkID(Long l) {
        // TODO Auto-generated method stub
        String[] columns=new String[]{KEY_ROWID,FIRST_NAME,LAST_NAME};
        Cursor c=myDatabase.query(DATABASE_TABLE, columns,null, null, null,null,null);
        int iRow=c.getColumnIndex(KEY_ROWID);


        for(c.moveToFirst();!c.isAfterLast();c.moveToNext()){
            Long l_id=Long.valueOf(c.getString(iRow));
            Log.v("L_id",""+l_id);
            if(l==l_id){
                return true;
            }
        }
        return false;

    }
    public void deleteEntry(Long lRow) {
        // TODO Auto-generated method stub
        myDatabase.delete(DATABASE_TABLE, KEY_ROWID+"="+lRow, null);
    }
}

主要的.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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/editText2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText1"
        android:layout_below="@+id/editText1"
        android:layout_marginTop="28dp"
        android:ems="10"
        android:hint="Last Name"
        android:inputType="textPersonName" />

    <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_alignRight="@+id/editText2"
        android:layout_marginRight="20dp"
        android:text="View" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/editText2"
        android:layout_marginRight="23dp"
        android:layout_marginTop="46dp"
        android:layout_toLeftOf="@+id/button2"
        android:text="Save" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="36dp"
        android:layout_marginTop="48dp"
        android:ems="10"
        android:hint="First Name"
        android:inputType="textPersonName" />

</RelativeLayout>

查看.java

package com.example.databaseexample;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class SQLView extends Activity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sqlview);
        TextView tv=(TextView) findViewById(R.id.tvSQLinfo);
        DBOperations info=new DBOperations(this);
        info.open();
        String data=info.getData();
        info.close();
        tv.setText(data);
    }

}

日志

   06-13 10:24:02.851: E/SQLiteLog(21041): (1) table persons_table has no column named last_name
06-13 10:24:02.899: E/SQLiteDatabase(21041): Error inserting last_name=dgsfg first_name=jimg
06-13 10:24:02.899: E/SQLiteDatabase(21041): android.database.sqlite.SQLiteException: table persons_table has no column named last_name (code 1): , while compiling: INSERT INTO persons_table(last_name,first_name) VALUES (?,?)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1467)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1339)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at com.example.db.dbclas.createEntry(dbclas.java:63)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at com.example.db.MainActivity$1.onClick(MainActivity.java:41)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.view.View.performClick(View.java:4204)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.view.View$PerformClick.run(View.java:17355)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.os.Handler.handleCallback(Handler.java:725)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.os.Looper.loop(Looper.java:137)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at android.app.ActivityThread.main(ActivityThread.java:5041)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at java.lang.reflect.Method.invokeNative(Native Method)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at java.lang.reflect.Method.invoke(Method.java:511)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-13 10:24:02.899: E/SQLiteDatabase(21041):    at dalvik.system.NativeStart.main(Native Method)
4

2 回答 2

1

您的数据库助手对我来说看起来不错。您收到空异常错误，因为 fname 和 lname 为空。

b1.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        String f=e1.getText().toString();
        String l =e2.getText().toString();
        if(checkForNotEmpty(fname, lname)){ // replace fname and lname with f and l here
            try{
                dbclas entry =new dbclas(MainActivity.this);
            entry.open();
            entry.createEntry(fname,lname);
            entry.close();
            }catch (Exception e) {
                // TODO: handle exception
                showMyDialog("Error", e.toString());
            }

        }
    Toast.makeText(getApplicationContext(),"Saved", 0).show();  
    }
});

应该是

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        String f=e1.getText().toString();
        String l =e2.getText().toString();
           String f=e1.getText().toString();
            String l =e2.getText().toString();
            if(checkForNotEmpty(f, l)){
....
}
于 2013-06-13T09:27:03.723 回答
1

你的字符串对象中的小错误看看这个使用这个

fname = e1.getText().toString();
lname = e2.getText().toString();

代替

String f = e1.getText().toString();
String l = e2.getText().toString();
于 2013-06-13T09:30:05.103 回答