家庭小账本——数据库的编写与测试

　　今天尝试了家庭小账本的数据库创建并且测试，但是在写完代码运行测试的时候软件闪退，修改了好长时间并没有成功，可能是因为作为初学者有很多地方并不是清晰地了解，修改的地方也不是很准确，做了很多的无用功，但是今天这次毕竟是一个尝试。

　　先创建了DataBaseHelper的类，进行数据库的创建，添加以及其他的操作。

  1 package com.example.familyledger;
  2 
  3 import android.database.Cursor;
  4 import android.os.Bundle;
  5 
  6 import com.google.android.material.floatingactionbutton.FloatingActionButton;
  7 import com.google.android.material.snackbar.Snackbar;
  8 
  9 import androidx.appcompat.app.AppCompatActivity;
 10 import androidx.appcompat.widget.Toolbar;
 11 
 12 import android.view.View;
 13 import android.view.Menu;
 14 import android.view.MenuItem;
 15 import android.widget.ListView;
 16 
 17 import java.util.ArrayList;
 18 import java.util.List;
 19 
 20 import androidx.appcompat.app.AppCompatActivity;
 21 
 22 import android.database.sqlite.SQLiteOpenHelper;
 23 import android.os.Bundle;
 24 import android.content.Context;
 25 import android.database.sqlite.SQLiteDatabase;
 26 import android.database.sqlite.SQLiteDatabase.CursorFactory;
 27 import android.database.sqlite.SQLiteException;
 28 import android.util.Log;
 29 
 30 public class MainActivity extends AppCompatActivity {
 31 
 32     private List<CostBean> mCostListBean;
 33     private DataBaseHelper mDataBaseHelper;
 34     @Override
 35     protected void onCreate(Bundle savedInstanceState) {
 36         super.onCreate(savedInstanceState);
 37         setContentView(R.layout.activity_main);
 38         Toolbar toolbar = findViewById(R.id.toolbar);
 39         setSupportActionBar(toolbar);
 40 
 41 
 42         mDataBaseHelper=new DataBaseHelper(this);
 43         mCostListBean=new ArrayList<>();
 44         ListView costList=(ListView)findViewById(R.id.lv_main);
 45         initCostdata();
 46         costList.setAdapter(new CostListAdapter(this,mCostListBean));
 47 
 48 
 49         FloatingActionButton fab = findViewById(R.id.fab);
 50         fab.setOnClickListener(new View.OnClickListener() {
 51             @Override
 52             public void onClick(View view) {
 53                 Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
 54                         .setAction("Action", null).show();
 55             }
 56         });
 57     }
 58 
 59     private void initCostdata() {
 60         for (int i=0;i<6;i++) {
 61             CostBean costBean=new CostBean();
 62             costBean.costDate="11-11";
 63             costBean.costMoney="20";
 64             costBean.costTitle=i+"mock";
 65             mDataBaseHelper.insertCost(costBean);
 66         }
 67         Cursor cursor =mDataBaseHelper.getAllCostData();
 68         if(cursor!=null)
 69         {
 70             while (cursor.moveToNext()){
 71                 CostBean costBean=new CostBean();
 72                 costBean.costTitle=cursor.getString(cursor.getColumnIndex("cost_title"));
 73                 costBean.costDate=cursor.getString(cursor.getColumnIndex("cost_date"));
 74                 costBean.costMoney=cursor.getString(cursor.getColumnIndex("cost_money"));
 75                 mCostListBean.add(costBean);
 76             }
 77             cursor.close();
 78         }
 79     }
 80 
 81     @Override
 82     public boolean onCreateOptionsMenu(Menu menu) {
 83         // Inflate the menu; this adds items to the action bar if it is present.
 84         getMenuInflater().inflate(R.menu.menu_main, menu);
 85         return true;
 86     }
 87 
 88     @Override
 89     public boolean onOptionsItemSelected(MenuItem item) {
 90         // Handle action bar item clicks here. The action bar will
 91         // automatically handle clicks on the Home/Up button, so long
 92         // as you specify a parent activity in AndroidManifest.xml.
 93         int id = item.getItemId();
 94 
 95         //noinspection SimplifiableIfStatement
 96         if (id == R.id.action_settings) {
 97             return true;
 98         }
 99 
100         return super.onOptionsItemSelected(item);
101     }
102 }

然后在MainActivity中添加关于创建数据库操作的代码，这时候数据库中已经存在了几天数据（上述代码），但是添加完之后并不能运行，修改多次也不行，今天只能这样结束了。

  1 package com.example.familyledger;
  2 
  3 import android.database.Cursor;
  4 import android.os.Bundle;
  5 
  6 import com.google.android.material.floatingactionbutton.FloatingActionButton;
  7 import com.google.android.material.snackbar.Snackbar;
  8 
  9 import androidx.appcompat.app.AppCompatActivity;
 10 import androidx.appcompat.widget.Toolbar;
 11 
 12 import android.view.View;
 13 import android.view.Menu;
 14 import android.view.MenuItem;
 15 import android.widget.ListView;
 16 
 17 import java.util.ArrayList;
 18 import java.util.List;
 19 
 20 import androidx.appcompat.app.AppCompatActivity;
 21 
 22 import android.database.sqlite.SQLiteOpenHelper;
 23 import android.os.Bundle;
 24 import android.content.Context;
 25 import android.database.sqlite.SQLiteDatabase;
 26 import android.database.sqlite.SQLiteDatabase.CursorFactory;
 27 import android.database.sqlite.SQLiteException;
 28 import android.util.Log;
 29 
 30 public class MainActivity extends AppCompatActivity {
 31 
 32     private List<CostBean> mCostListBean;
 33     private DataBaseHelper mDataBaseHelper;
 34     @Override
 35     protected void onCreate(Bundle savedInstanceState) {
 36         super.onCreate(savedInstanceState);
 37         setContentView(R.layout.activity_main);
 38         Toolbar toolbar = findViewById(R.id.toolbar);
 39         setSupportActionBar(toolbar);
 40 
 41 
 42         mDataBaseHelper=new DataBaseHelper(this);
 43         mCostListBean=new ArrayList<>();
 44         ListView costList=(ListView)findViewById(R.id.lv_main);
 45         initCostdata();
 46         costList.setAdapter(new CostListAdapter(this,mCostListBean));
 47 
 48 
 49         FloatingActionButton fab = findViewById(R.id.fab);
 50         fab.setOnClickListener(new View.OnClickListener() {
 51             @Override
 52             public void onClick(View view) {
 53                 Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
 54                         .setAction("Action", null).show();
 55             }
 56         });
 57     }
 58 
 59     private void initCostdata() {
 60         for (int i=0;i<6;i++) {
 61             CostBean costBean=new CostBean();
 62             costBean.costDate="11-11";
 63             costBean.costMoney="20";
 64             costBean.costTitle=i+"mock";
 65             mDataBaseHelper.insertCost(costBean);
 66         }
 67         Cursor cursor =mDataBaseHelper.getAllCostData();
 68         if(cursor!=null)
 69         {
 70             while (cursor.moveToNext()){
 71                 CostBean costBean=new CostBean();
 72                 costBean.costTitle=cursor.getString(cursor.getColumnIndex("cost_title"));
 73                 costBean.costDate=cursor.getString(cursor.getColumnIndex("cost_date"));
 74                 costBean.costMoney=cursor.getString(cursor.getColumnIndex("cost_money"));
 75                 mCostListBean.add(costBean);
 76             }
 77             cursor.close();
 78         }
 79     }
 80 
 81     @Override
 82     public boolean onCreateOptionsMenu(Menu menu) {
 83         // Inflate the menu; this adds items to the action bar if it is present.
 84         getMenuInflater().inflate(R.menu.menu_main, menu);
 85         return true;
 86     }
 87 
 88     @Override
 89     public boolean onOptionsItemSelected(MenuItem item) {
 90         // Handle action bar item clicks here. The action bar will
 91         // automatically handle clicks on the Home/Up button, so long
 92         // as you specify a parent activity in AndroidManifest.xml.
 93         int id = item.getItemId();
 94 
 95         //noinspection SimplifiableIfStatement
 96         if (id == R.id.action_settings) {
 97             return true;
 98         }
 99 
100         return super.onOptionsItemSelected(item);
101     }
102 }

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原文地址：https://www.cnblogs.com/2940500426yingxin/p/12296315.html