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：

  1 package com.example.daily;
  2 
  3 import android.content.DialogInterface;
  4 import android.content.Intent;
  5 import android.database.Cursor;
  6 import android.os.Bundle;
  7 
  8 import com.google.android.material.floatingactionbutton.FloatingActionButton;
  9 import com.google.android.material.snackbar.Snackbar;
 10 
 11 import androidx.appcompat.app.AlertDialog;
 12 import androidx.appcompat.app.AppCompatActivity;
 13 import androidx.appcompat.widget.Toolbar;
 14 
 15 import android.text.Layout;
 16 import android.view.LayoutInflater;
 17 import android.view.View;
 18 import android.view.Menu;
 19 import android.view.MenuItem;
 20 import android.widget.Button;
 21 import android.widget.DatePicker;
 22 import android.widget.EditText;
 23 import android.widget.ListView;
 24 
 25 import java.io.Serializable;
 26 import java.util.ArrayList;
 27 import java.util.List;
 28 
 29 public class MainActivity extends AppCompatActivity {
 30 
 31     private List<CostBean> mCostBeanList;
 32     private DatabaseHelper mDatabaseHelper;
 33     private CostListAdapter mAdapter;
 34 
 35     @Override
 36     protected void onCreate(Bundle savedInstanceState) {
 37         super.onCreate(savedInstanceState);
 38         setContentView(R.layout.activity_main);
 39         Toolbar toolbar = findViewById(R.id.toolbar);
 40         setSupportActionBar(toolbar);
 41         mDatabaseHelper = new DatabaseHelper(this,"daily",null,1);
 42         mCostBeanList = new ArrayList<>();
 43         ListView costList = findViewById(R.id.lv_main);
 44         initCostData();
 45         mAdapter = new CostListAdapter(this, mCostBeanList);
 46         costList.setAdapter(mAdapter);
 47 
 48         FloatingActionButton fab = findViewById(R.id.fab);
 49         fab.setOnClickListener(new View.OnClickListener() {
 50             @Override
 51             public void onClick(View view) {
 52                 AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
 53                 LayoutInflater inflater = LayoutInflater.from(MainActivity.this);
 54                 View viewDiaglog = inflater.inflate(R.layout.new_cost_data,null);
 55                 final EditText title = viewDiaglog.findViewById(R.id.et_cost_title);
 56                 final EditText money = viewDiaglog.findViewById(R.id.et_cost_money);
 57                 final DatePicker date  = viewDiaglog.findViewById(R.id.dp_cost_data);
 58                 builder.setView(viewDiaglog);
 59                 builder.setTitle("新的消费项");
 60                 builder.setPositiveButton("添加", new DialogInterface.OnClickListener() {
 61                     @Override
 62                     public void onClick(DialogInterface dialog, int which) {
 63                             CostBean costBean = new CostBean();
 64                             costBean.costTitle = title.getText().toString();
 65                             costBean.costMoney = money.getText().toString();
 66                             costBean.costDate = date.getYear() + "-" + (date.getMonth()+1)+"-" + date.getDayOfMonth();
 67                             mDatabaseHelper.insertCost(costBean);
 68                             mCostBeanList.add(costBean);
 69                             mAdapter.notifyDataSetChanged();
 70                     }
 71                 });
 72                 builder.setNegativeButton("取消",null);
 73                 builder.create().show();
 74             }
 75         });
 76         Button delbtn = findViewById(R.id.deleteCost);
 77 
 78     }
 79 
 80     private void initCostData() {
 81 //        mDatabaseHelper.deleteAllData();
 82 //        for (int i = 0;i<6;i++) {
 83 //            CostBean costBean = new CostBean();
 84 //            costBean.costTitle = i + "mock";
 85 //            costBean.costDate = "11-11";
 86 //            costBean.costMoney = "20";
 87 //           mDatabaseHelper.insertCost(costBean);
 88 //        }
 89 
 90         Cursor cursor = mDatabaseHelper.getAllCostData();
 91         if(cursor!=null){
 92             while(cursor.moveToNext()){
 93                 CostBean costBean = new CostBean();
 94                 costBean.costTitle = cursor.getString(cursor.getColumnIndex("cost_title"));
 95                 costBean.costDate = cursor.getString(cursor.getColumnIndex("cost_date"));
 96                 costBean.costMoney = cursor.getString(cursor.getColumnIndex("cost_money"));
 97                 mCostBeanList.add(costBean);
 98             }
 99             cursor.close();
100         }
101 
102     }
103 
104     @Override
105     public boolean onCreateOptionsMenu(Menu menu) {
106         // Inflate the menu; this adds items to the action bar if it is present.
107         getMenuInflater().inflate(R.menu.menu_main, menu);
108         return true;
109     }
110 
111     @Override
112     public boolean onOptionsItemSelected(MenuItem item) {
113         int id = item.getItemId();
114         if (id == R.id.action_chart) {
115             Intent intent = new Intent(MainActivity.this,ChartActivity.class);
116             intent.putExtra("cost_list", (Serializable) mCostBeanList);
117             startActivity(intent);
118             return true;
119         }
120 
121         return super.onOptionsItemSelected(item);
122     }
123 }

MainActivity

 1 package com.example.daily;
 2 
 3 import android.content.Context;
 4 import android.view.LayoutInflater;
 5 import android.view.View;
 6 import android.view.ViewGroup;
 7 import android.widget.BaseAdapter;
 8 import android.widget.Button;
 9 import android.widget.TextView;
10 
11 import org.w3c.dom.Text;
12 
13 import java.util.List;
14 
15 public class CostListAdapter extends BaseAdapter{
16     private List<CostBean> mList;
17     private Context mContext;
18     private LayoutInflater mLayoutInflater;
19     public CostListAdapter(Context context, List<CostBean> list){
20         mContext = context;
21         mList = list;
22         mLayoutInflater = LayoutInflater.from(context);
23     }
24 
25 
26 
27     @Override
28     public int getCount() {
29         return mList.size();
30     }
31 
32     @Override
33     public Object getItem(int position) {
34         return mList.get(position);
35     }
36 
37     @Override
38     public long getItemId(int position) {
39         return position;
40     }
41 
42     @Override
43     public View getView(int position, View convertView, ViewGroup parent) {
44         ViewHolder viewHolder;
45         if(convertView==null){
46             viewHolder = new ViewHolder();
47             convertView = mLayoutInflater.inflate(R.layout.list_item,null);
48             viewHolder.mTvCostTitle =  convertView.findViewById(R.id.tv_title);
49             viewHolder.mTvCostDate = convertView.findViewById(R.id.tv_date);
50             viewHolder.mTvCostMoney = convertView.findViewById(R.id.tv_cost);
51             convertView.setTag(viewHolder);
52         }else{
53             viewHolder = (ViewHolder) convertView.getTag();
54         }
55         CostBean bean = mList.get(position);
56         viewHolder.mTvCostTitle.setText(bean.costTitle);
57         viewHolder.mTvCostDate.setText(bean.costDate);
58         viewHolder.mTvCostMoney.setText(bean.costMoney);
59         return convertView;
60     }
61     private  static class ViewHolder{
62         public TextView mTvCostTitle;
63         public TextView mTvCostDate;
64         public TextView mTvCostMoney;
65     }
66 
67 }

CostListAdaper

 1 package com.example.daily;
 2 
 3 import android.content.ContentValues;
 4 import android.content.Context;
 5 import android.database.Cursor;
 6 import android.database.sqlite.SQLiteDatabase;
 7 import android.database.sqlite.SQLiteOpenHelper;
 8 
 9 import androidx.annotation.Nullable;
10 
11 public class DatabaseHelper  extends SQLiteOpenHelper {
12 
13     public static final String COST_MONEY = "cost_money";
14     public static final String COST_DATE = "cost_date";
15     public static final String COST_TITLE = "cost_title";
16     public static final String COST = "cost";
17     public DatabaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
18         super(context, "daily", null, 1);
19     }
20 
21     @Override
22     public void onCreate(SQLiteDatabase db) {
23         db.execSQL("create table if not exists cost(" +
24                 "id integer primary key AUTOINCREMENT," +
25                 "cost_title varchar," +
26                 "cost_date varchar," +
27                 "cost_money varchar)");
28     }
29     public void insertCost(CostBean costBean){
30         SQLiteDatabase database = getWritableDatabase();
31         ContentValues cv  = new ContentValues();
32         cv.put(COST_TITLE,costBean.costTitle);
33         cv.put(COST_DATE,costBean.costDate);
34         cv.put(COST_MONEY,costBean.costMoney);
35         database.insert(COST,null,cv);
36     }
37     public Cursor getAllCostData(){
38         SQLiteDatabase database = getWritableDatabase();
39         return database.query(COST,null,null,null,null,null,COST_DATE+" ASC");
40 
41     }
42     public void deleteAllData(){
43         SQLiteDatabase database = getWritableDatabase();
44         database.delete(COST,null,null);
45     }
46     public void deleteCost(int id){
47         SQLiteDatabase database = getWritableDatabase();
48         database.delete(COST,"id=?",new String[]{"id"});
49     }
50     @Override
51     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
52 
53     }
54 }

其他的代码都大同小异也不再贴了

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