SQL增删

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这次的作业没有完成有好多错误，对于数据库还是不会运用。运行都是报错。
1.简单的布局
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.administrator.sqlzs.MainActivity">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"/>
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="增加新记录"
            android:textSize="25sp"
            android:id="@+id/btn_add"/>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="删除第一条记录"
            android:textSize="25sp"
            android:id="@+id/btn_del"/>

    </LinearLayout>
    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/listview">

    </ListView>
</LinearLayout>
2.java   
package com.example.administrator.sqlzs;

import android.content.ContentValues;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    private MySqlDataHelper helper;
    private Button btn_add;
    private Button btn_del;
    private int contentView;

    @Override
    public void onCreate(Bundle savedInstanceState, Object view) {
        super.onCreate(savedInstanceState, view);
        setContentView(R.layout.activity_main);
        Object newView;{
            @Override
            public void onClick(View view){
                helper.getWritableDatabase();
                }
            };
        btn_add = ((Button) btn_add.findViewById(R.id.btn_add));;
        btn_add.setOnClickListener(new View.OnClickListener() {
            public int contentView;

            @Override
            public void onClick(View view) {
                SQLiteDatabase db = helper.getWritableDatabase();
                ContentValues values = new ContentValues();
                db.insert("Book", null, values);
                values.clear();

                btn_del = ((Button) view.findViewById(R.id.btn_del));
                btn_del.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        SQLiteDatabase db = helper.getWritableDatabase();
                        db.delete("Book", "pages > ?", new String[]{"500"});
                    }
                });
            }