安卓开发学习01

写在前面：

今天是学习的第一天 姑且照着网上的视频教程敲了一个简单的代码 但完全不理解其中的意思 效果也算是实现了，如图：

 目前只实现了增的功能 删和改在网上查阅了半天资料还是没能想通该怎么写 下面贴一下代码：

package com.example.daily;

import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;

import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.text.Layout;
import android.view.LayoutInflater;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.ListView;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private List<CostBean> mCostBeanList;
    private DatabaseHelper mDatabaseHelper;
    private CostListAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        mDatabaseHelper = new DatabaseHelper(this,"daily",null,1);
        mCostBeanList = new ArrayList<>();
        ListView costList = findViewById(R.id.lv_main);
        initCostData();
        mAdapter = new CostListAdapter(this, mCostBeanList);
        costList.setAdapter(mAdapter);

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                LayoutInflater inflater = LayoutInflater.from(MainActivity.this);
                View viewDiaglog = inflater.inflate(R.layout.new_cost_data,null);
                final EditText title = viewDiaglog.findViewById(R.id.et_cost_title);
                final EditText money = viewDiaglog.findViewById(R.id.et_cost_money);
                final DatePicker date  = viewDiaglog.findViewById(R.id.dp_cost_data);
                builder.setView(viewDiaglog);
                builder.setTitle("新的消费项");
                builder.setPositiveButton("添加", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                            CostBean costBean = new CostBean();
                            costBean.costTitle = title.getText().toString();
                            costBean.costMoney = money.getText().toString();
                            costBean.costDate = date.getYear() + "-" + (date.getMonth()+1)+"-" + date.getDayOfMonth();
                            mDatabaseHelper.insertCost(costBean);
                            mCostBeanList.add(costBean);
                            mAdapter.notifyDataSetChanged();
                    }
                });
                builder.setNegativeButton("取消",null);
                builder.create().show();
            }
        });
        Button delbtn = findViewById(R.id.deleteCost);

    }

    private void initCostData() {
//        mDatabaseHelper.deleteAllData();
//        for (int i = 0;i<6;i++) {
//            CostBean costBean = new CostBean();
//            costBean.costTitle = i + "mock";
//            costBean.costDate = "11-11";
//            costBean.costMoney = "20";
//           mDatabaseHelper.insertCost(costBean);
//        }

        Cursor cursor = mDatabaseHelper.getAllCostData();
        if(cursor!=null){
            while(cursor.moveToNext()){
                CostBean costBean = new CostBean();
                costBean.costTitle = cursor.getString(cursor.getColumnIndex("cost_title"));
                costBean.costDate = cursor.getString(cursor.getColumnIndex("cost_date"));
                costBean.costMoney = cursor.getString(cursor.getColumnIndex("cost_money"));
                mCostBeanList.add(costBean);
            }
            cursor.close();
        }

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.action_chart) {
            Intent intent = new Intent(MainActivity.this,ChartActivity.class);
            intent.putExtra("cost_list", (Serializable) mCostBeanList);
            startActivity(intent);
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

package com.example.daily;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.TextView;

import org.w3c.dom.Text;

import java.util.List;

public class CostListAdapter extends BaseAdapter{
    private List<CostBean> mList;
    private Context mContext;
    private LayoutInflater mLayoutInflater;
    public CostListAdapter(Context context, List<CostBean> list){
        mContext = context;
        mList = list;
        mLayoutInflater = LayoutInflater.from(context);
    }



    @Override
    public int getCount() {
        return mList.size();
    }

    @Override
    public Object getItem(int position) {
        return mList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if(convertView==null){
            viewHolder = new ViewHolder();
            convertView = mLayoutInflater.inflate(R.layout.list_item,null);
            viewHolder.mTvCostTitle =  convertView.findViewById(R.id.tv_title);
            viewHolder.mTvCostDate = convertView.findViewById(R.id.tv_date);
            viewHolder.mTvCostMoney = convertView.findViewById(R.id.tv_cost);
            convertView.setTag(viewHolder);
        }else{
            viewHolder = (ViewHolder) convertView.getTag();
        }
        CostBean bean = mList.get(position);
        viewHolder.mTvCostTitle.setText(bean.costTitle);
        viewHolder.mTvCostDate.setText(bean.costDate);
        viewHolder.mTvCostMoney.setText(bean.costMoney);
        return convertView;
    }
    private  static class ViewHolder{
        public TextView mTvCostTitle;
        public TextView mTvCostDate;
        public TextView mTvCostMoney;
    }

}

package com.example.daily;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

public class DatabaseHelper  extends SQLiteOpenHelper {

    public static final String COST_MONEY = "cost_money";
    public static final String COST_DATE = "cost_date";
    public static final String COST_TITLE = "cost_title";
    public static final String COST = "cost";
    public DatabaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, "daily", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table if not exists cost(" +
                "id integer primary key AUTOINCREMENT," +
                "cost_title varchar," +
                "cost_date varchar," +
                "cost_money varchar)");
    }
    public void insertCost(CostBean costBean){
        SQLiteDatabase database = getWritableDatabase();
        ContentValues cv  = new ContentValues();
        cv.put(COST_TITLE,costBean.costTitle);
        cv.put(COST_DATE,costBean.costDate);
        cv.put(COST_MONEY,costBean.costMoney);
        database.insert(COST,null,cv);
    }
    public Cursor getAllCostData(){
        SQLiteDatabase database = getWritableDatabase();
        return database.query(COST,null,null,null,null,null,COST_DATE+" ASC");

    }
    public void deleteAllData(){
        SQLiteDatabase database = getWritableDatabase();
        database.delete(COST,null,null);
    }
    public void deleteCost(int id){
        SQLiteDatabase database = getWritableDatabase();
        database.delete(COST,"id=?",new String[]{"id"});
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

其他的代码都大同小异 也不再贴了