Android学习中关于SQLite的一个小Demo（数据库的创建、数据的增删查改）

来源：Andr_Robot 发布时间：2018-11-30 17:41:15 阅读量：964

最近学习Android，做了一些小的东西，一直没有时间做个总结。经常总结对于学习新东西是很好的，说以今天整理一下自己做的东西，希望这样也有助于其他人学习。

我做的是一个基于Android平台，使用SQLite构建数据库，并且创建表来存储数据，还会涉及到数据的增删查改。整体的效果图如下：

上面就是Demo在调试时的几幅图，下面将会一一介绍这个Demo中用到的一些核心技术。

首先就是用到了SQLiteOpenHelper这个类，通过创建一个自己的帮助类来继承这个抽象类，来实现简单的对数据库创建和升级。SQLiteOpenHelper中有两个抽象方法，分别是onCreate()和onUpgrade()，我们必须在自己的帮助类里面重写这两个方法，然后分别在这两个方法中去实现创建、升级数据库的逻辑。SQLiteOpenHelper中有两个非常重要的实例方法，getReadableDatabase()和getWritableDatabase()。这两个方法都可以创建和打开一个现有的数据库（如果数据库已经存在则直接打开，否则创建一个新的数据库），并返回一个可对数据库进行读写操作的对象。不同的是，当数据库不可写入的时候（如磁盘空间已满）getReadabelDatabase()方法返回的对象将以只读的方式去打开数据库，而getWritableDatabase()方法则会出现异常。

MyDatabaseHelper.java

public class MyDatabaseHelper extends SQLiteOpenHelper {

private static final String CREATE_TABLE = "create table peopleinfo (_id integer primary key autoincrement,name text not null,age integer,height float);";

private Context mContext;

public MyDatabaseHelper(Context context, String name,

CursorFactory factory, int version) {

super(context, name, factory, version);

mContext = context;

}

@Override

public void onCreate(SQLiteDatabase db) {

db.execSQL(CREATE_TABLE);

}

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

db.execSQL("drop table if exists peopleinfo");

onCreate(db);

}

“drop table if exists peopleinfo”这句代码的作用就是当发现数据库中已经存在peopleinfo表，就将这两个表删除掉，然后调用onCreate()方法去重新创建。

构建People用来存储输入的People信息，方便向数据库中存储。

People.java

public class People {

public int ID;

public String Name;

public int Age;

public float Height;

public int getID() {

return ID;

}

public void setID(int iD) {

ID = iD;

}

public String getName() {

return Name;

}

public void setName(String name) {

Name = name;

}

public int getAge() {

return Age;

}

public void setAge(int age) {

Age = age;

}

public float getHeight() {

return Height;

}

public void setHeight(float height) {

Height = height;

}

@Override

public String toString(){

String result = "";

result += "ID：" + this.ID + "，";

result += "姓名：" + this.Name + "，";

result += "年龄：" + this.Age + "， ";

result += "身高：" + this.Height ;

return result;

}

activity_main.xml:主界面的布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical">

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal"

android:layout_margin="10dp">

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="姓名："

android:textSize="23sp"/>

<EditText

android:id="@+id/edt_name"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="请输入姓名"/>

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal"

android:layout_marginLeft="10dp"

android:layout_marginRight="10dp">

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="年龄："

android:textSize="23sp"/>

<EditText

android:id="@+id/edt_age"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:numeric="integer"

android:hint="请输入年龄"/>

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal"

android:layout_marginTop="10dp"

android:layout_marginLeft="10dp"

android:layout_marginRight="10dp">

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="身高："

android:textSize="23sp"/>

<EditText

android:id="@+id/edt_height"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:numeric="decimal"

android:hint="请输入身高"/>

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginLeft="10dp"

android:layout_marginRight="10dp"

android:layout_marginTop="10dp"

android:orientation="horizontal">

<Button

android:id="@+id/bt_adddata"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="添加数据"

android:textSize="12sp"

android:layout_weight="1"/>

<Button

android:id="@+id/bt_showalldata"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="全部显示"

android:textSize="12sp"

android:layout_weight="1"/>

<Button

android:id="@+id/bt_clearshowdata"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="清除显示"

android:textSize="12sp"

android:layout_weight="1"/>

<Button

android:id="@+id/bt_deletealldata"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="全部删除"

android:textSize="12sp"

android:layout_weight="1"/>

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginLeft="10dp"

android:layout_marginTop="10dp"

android:layout_marginRight="10dp"

android:orientation="horizontal">

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="ID:"

android:textSize="23sp"/>

<EditText

android:id="@+id/edt_id"

android:layout_width="40dp"

android:layout_height="wrap_content"

android:numeric="integer"

android:layout_weight="1"/>

<Button

android:id="@+id/bt_deteleid"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="ID删除"

android:textSize="12sp"

android:layout_weight="1"/>

<Button

android:id="@+id/bt_queryid"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="ID查询"

android:textSize="12sp"

android:layout_weight="1"/>

<Button

android:id="@+id/bt_updateid"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="ID更新"

android:textSize="12sp"

android:layout_weight="1"/>

</LinearLayout>

<TextView

android:layout_margin="10dp"

android:id="@+id/txt_sjk"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="数据库："

android:textSize="23sp"/>

<ListView

android:layout_marginLeft="10dp"

android:layout_marginRight="10dp"

android:id="@+id/listview_show"

android:layout_width="match_parent"

android:layout_height="wrap_content"/>

</LinearLayout>

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MainActivity.java

public class MainActivity extends Activity implements OnClickListener {

private MyDatabaseHelper dbHelper;

private SQLiteDatabase db;

private EditText edt_Name;

private EditText edt_Age;

private EditText edt_Height;

private EditText edt_Id;

private Button bt_AddData;

private Button bt_ShowAllData;

private Button bt_ClearShowData;

private Button bt_DeleteAllData;

private Button bt_DeleteById;

private Button bt_QueryById;

private Button bt_UpdateById;

private ListView listview_show;

private String strName = "";

private String strAge = "";

private String strHeight = "";

private int m_Id;

private List<People> PeopleList = new ArrayList<People>();

private MyAdapter mAdapter;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

dbHelper = new MyDatabaseHelper(this, "people.db", null, 1);

db = dbHelper.getWritableDatabase();

// 初始化控件

initShow();

// 添加数据

bt_AddData.setOnClickListener(this);

// 全部显示

bt_ShowAllData.setOnClickListener(this);

// 清楚显示

bt_ClearShowData.setOnClickListener(this);

// 全部删除

bt_DeleteAllData.setOnClickListener(this);

// ID删除

bt_DeleteById.setOnClickListener(this);

// ID查询

bt_QueryById.setOnClickListener(this);

// ID更新

bt_UpdateById.setOnClickListener(this);

}

// 初始化控件

private void initShow() {

edt_Name = (EditText) findViewById(R.id.edt_name);

edt_Age = (EditText) findViewById(R.id.edt_age);

edt_Height = (EditText) findViewById(R.id.edt_height);

edt_Id = (EditText) findViewById(R.id.edt_id);

bt_AddData = (Button) findViewById(R.id.bt_adddata);

bt_ShowAllData = (Button) findViewById(R.id.bt_showalldata);

bt_ClearShowData = (Button) findViewById(R.id.bt_clearshowdata);

bt_DeleteAllData = (Button) findViewById(R.id.bt_deletealldata);

bt_DeleteById = (Button) findViewById(R.id.bt_deteleid);

bt_QueryById = (Button) findViewById(R.id.bt_queryid);

bt_UpdateById = (Button) findViewById(R.id.bt_updateid);

listview_show = (ListView) findViewById(R.id.listview_show);

}

// listview显示数据库数据

private void showData() {

mAdapter = new MyAdapter(MainActivity.this,

android.R.layout.simple_list_item_1, PeopleList);

listview_show.setAdapter(mAdapter);

}

// 获取edittext中输入的ID

public int getEd_ID() {

if (!edt_Id.getText().toString().equals("")) {

String strId = edt_Id.getText().toString();

m_Id = Integer.parseInt(strId);

} else {

m_Id = -1;

}

return m_Id;

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

getMenuInflater().inflate(R.menu.main, menu);

return true;

}

@Override

public boolean onOptionsItemSelected(MenuItem item) {

int id = item.getItemId();

if (id == R.id.action_settings) {

return true;

}

return super.onOptionsItemSelected(item);

}

@Override

public void onClick(View v) {

switch (v.getId()) {

// 添加数据

case R.id.bt_adddata:

addData();

edt_Name.setText("");

edt_Age.setText("");

edt_Height.setText("");

break;

// 全部显示

case R.id.bt_showalldata:

showAllData();

showData();

break;

// 清楚显示

case R.id.bt_clearshowdata:

clearListView();

showData();

break;

// 全部删除

case R.id.bt_deletealldata:

deleteData();

showData();

break;

// ID删除

case R.id.bt_deteleid:

m_Id = getEd_ID();

deleteById(m_Id);

showAllData();

showData();

edt_Id.setText("");

break;

// ID查询

case R.id.bt_queryid:

m_Id = getEd_ID();

queryById(m_Id);

showData();

edt_Id.setText("");

break;

// ID更新

case R.id.bt_updateid:

m_Id = getEd_ID();

updateById(m_Id);

showData();

edt_Id.setText("");

break;

}

// ID更新

private void updateById(int mId) {

if (mId == -1) {

Toast.makeText(MainActivity.this, "请输入ID号", Toast.LENGTH_SHORT)

.show();

} else {

// 先找到这条数据

db = dbHelper.getReadableDatabase();

final People people = new People();

List<People> tempList=new ArrayList<People>();

Cursor cursor = db.query("peopleinfo", null, "_id" + "=" + mId,

null, null, null, null);

if (cursor.moveToFirst()) {

do {

int id = cursor.getInt(cursor.getColumnIndex("_id"));

String name = cursor.getString(cursor

.getColumnIndex("name"));

int age = cursor.getInt(cursor.getColumnIndex("age"));

float height = cursor.getFloat(cursor

.getColumnIndex("height"));

people.setID(id);

people.setName(name);

people.setAge(age);

people.setHeight(height);

tempList.add(people);

} while (cursor.moveToNext());

}

cursor.close();

if (tempList.size()==0) {

Toast.makeText(MainActivity.this, "数据库中没有这条信息",

Toast.LENGTH_SHORT).show();

} else {

// 弹出自定义的AlertDialog

LayoutInflater factory = LayoutInflater.from(this);

final View textChangeView = factory.inflate(R.layout.custom,

null);

final EditText editTextName = (EditText) textChangeView

.findViewById(R.id.cEdt_name);

final EditText editTextAge = (EditText) textChangeView

.findViewById(R.id.cEdt_age);

final EditText editTextHeight = (EditText) textChangeView

.findViewById(R.id.cEdt_height);

editTextName.setText(people.getName());

editTextAge.setText(Integer.toString(people.getAge()));

editTextHeight.setText(Float.toString(people.getHeight()));

AlertDialog.Builder ad = new AlertDialog.Builder(

MainActivity.this);

ad.setTitle("ID更新：");

ad.setIcon(android.R.drawable.ic_dialog_info);

ad.setView(textChangeView);

ad.setPositiveButton("OK",

new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialog,

int which) {

ContentValues updateValues = new ContentValues();

strName = editTextName.getText().toString();

strAge = editTextAge.getText().toString();

strHeight = editTextHeight.getText().toString();

int iAge = Integer.parseInt(strAge);

float fHeight = Float.parseFloat(strHeight);

// 开始组装一条数据

updateValues.put("name", strName);

updateValues.put("age", iAge);

updateValues.put("height", fHeight);

db.update("peopleinfo", updateValues, "_id"

+ "=" + people.getID(), null);

Toast.makeText(MainActivity.this, "更新成功",

Toast.LENGTH_SHORT).show();

Cursor cursor = db.query("peopleinfo", null, "_id" + "=" + people.getID(),

null, null, null, null);

PeopleList.clear();

if (cursor.moveToFirst()) {

do {

int id = cursor.getInt(cursor.getColumnIndex("_id"));

String name = cursor.getString(cursor

.getColumnIndex("name"));

int age = cursor.getInt(cursor.getColumnIndex("age"));

float height = cursor.getFloat(cursor

.getColumnIndex("height"));

people.setID(id);

people.setName(name);

people.setAge(age);

people.setHeight(height);

PeopleList.add(people);

} while (cursor.moveToNext());

}

cursor.close();

}

});

ad.setNegativeButton("Cancel",

new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialog,

int which) {

}

});

ad.show();

}

// ID查询

private void queryById(int mId) {

if (mId == -1) {

Toast.makeText(MainActivity.this, "请输入ID号", Toast.LENGTH_SHORT)

.show();

} else {

db = dbHelper.getReadableDatabase();

People people = new People();

PeopleList.clear();

Cursor cursor = db.query("peopleinfo", null, "_id" + "=" + mId,

null, null, null, null);

if (cursor.moveToFirst()) {

do {

int id = cursor.getInt(cursor.getColumnIndex("_id"));

String name = cursor.getString(cursor

.getColumnIndex("name"));

int age = cursor.getInt(cursor.getColumnIndex("age"));

float height = cursor.getFloat(cursor

.getColumnIndex("height"));

people.setID(id);

people.setName(name);

people.setAge(age);

people.setHeight(height);

PeopleList.add(people);

} while (cursor.moveToNext());

}

cursor.close();

if (PeopleList.size() == 0) {

Toast.makeText(MainActivity.this, "数据库中没有这条数据",

Toast.LENGTH_SHORT).show();

}

// ID删除

private void deleteById(int mId) {

if (mId == -1) {

Toast.makeText(MainActivity.this, "请输入ID号", Toast.LENGTH_SHORT)

.show();

} else {

db = dbHelper.getWritableDatabase();

People people = new People();

PeopleList.clear();

Cursor cursor = db.query("peopleinfo", null, "_id" + "=" + mId,

null, null, null, null);

if (cursor.moveToFirst()) {

do {

int id = cursor.getInt(cursor.getColumnIndex("_id"));

String name = cursor.getString(cursor

.getColumnIndex("name"));

int age = cursor.getInt(cursor.getColumnIndex("age"));

float height = cursor.getFloat(cursor

.getColumnIndex("height"));

people.setID(id);

people.setName(name);

people.setAge(age);

people.setHeight(height);

PeopleList.add(people);

} while (cursor.moveToNext());

}

cursor.close();

if (PeopleList.size() == 0) {

Toast.makeText(MainActivity.this, "数据库中没有这条数据",

Toast.LENGTH_SHORT).show();

} else {

db.delete("peopleinfo", "_id" + "=" + mId, null);

Toast.makeText(MainActivity.this, "成功删除" + mId + "这条数据",

Toast.LENGTH_SHORT).show();

}

// 全部删除

private void deleteData() {

db = dbHelper.getWritableDatabase();

db.delete("peopleinfo", null, null);

PeopleList.clear();

Toast.makeText(MainActivity.this, "数据清除成功", Toast.LENGTH_SHORT).show();

}

// 清除显示

private void clearListView() {

PeopleList.clear();

}

// 全部显示

private void showAllData() {

PeopleList.clear();

Cursor cursor = db.query("peopleinfo", null, null, null, null, null,

null);

if (cursor.moveToFirst()) {

do {

People people = new People();

// 遍历表

int id = cursor.getInt(cursor.getColumnIndex("_id"));

String name = cursor.getString(cursor.getColumnIndex("name"));

int age = cursor.getInt(cursor.getColumnIndex("age"));

float height = cursor.getFloat(cursor.getColumnIndex("height"));

people.setID(id);

people.setName(name);

people.setAge(age);

people.setHeight(height);

PeopleList.add(people);

} while (cursor.moveToNext());

}

cursor.close();

if (PeopleList.size() == 0) {

Toast.makeText(MainActivity.this, "数据库中没有数据", Toast.LENGTH_SHORT)

.show();

}

// 添加数据

private void addData() {

if (edt_Name.getText().toString().equals("")

&& edt_Age.getText().toString().equals("")

&& edt_Height.getText().toString().equals("")) {

AlertDialog.Builder dialog = new AlertDialog.Builder(

MainActivity.this);

dialog.setTitle("Warn");

dialog.setMessage("请输入完整信息");

dialog.setCancelable(false);

dialog.setPositiveButton("OK",

new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialog, int which) {

edt_Name.setText("");

edt_Age.setText("");

edt_Height.setText("");

}

});

dialog.show();

} else {

ContentValues values = new ContentValues();

strName = edt_Name.getText().toString();

strAge = edt_Age.getText().toString();

strHeight = edt_Height.getText().toString();

int iAge = Integer.parseInt(strAge);

float fHeight = Float.parseFloat(strHeight);

// 开始组装一条数据

values.put("name", strName);

values.put("age", iAge);

values.put("height", fHeight);

// 插入数据

db.insert("peopleinfo", null, values);

Toast.makeText(MainActivity.this, "数据添加成功", Toast.LENGTH_SHORT)

.show();

}

@Override

public boolean dispatchTouchEvent(MotionEvent ev) {

// TODO Auto-generated method stub

if (ev.getAction() == MotionEvent.ACTION_DOWN) {

// 获得当前得到焦点的View，一般情况下就是EditText（特殊情况就是轨迹求或者实体案件会移动焦点）

View v = getCurrentFocus();

if (isShouldHideInput(v, ev)) {

hideSoftInput(v.getWindowToken());

}

return super.dispatchTouchEvent(ev);

}

/**

* 根据EditText所在坐标和用户点击的坐标相对比，来判断是否隐藏键盘，因为当用户点击EditText时没必要隐藏

* @param v

* @param event

* @return

private boolean isShouldHideInput(View v, MotionEvent event) {

if (v != null && (v instanceof EditText)) {

int[] l = { 0, 0 };

v.getLocationInWindow(l);

int left = l[0], top = l[1], bottom = top + v.getHeight(), right = left

+ v.getWidth();

if (event.getX() > left && event.getX() < right

&& event.getY() > top && event.getY() < bottom) {

// 点击EditText的事件，忽略它。

return false;

} else {

return true;

}

// 如果焦点不是EditText则忽略，这个发生在视图刚绘制完，第一个焦点不在EditView上，和用户用轨迹球选择其他的焦点

return false;

}

/**

* 多种隐藏软件盘方法的其中一种

* @param token

private void hideSoftInput(IBinder token) {

if (token != null) {

InputMethodManager im = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);

im.hideSoftInputFromWindow(token,

InputMethodManager.HIDE_NOT_ALWAYS);

}

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custom.xml:自定义布局文件，用在ID更新时弹出的AlertDialog中。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical" >

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_margin="10dp"

android:orientation="horizontal" >

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="姓名："

android:textSize="23sp" />

<EditText

android:id="@+id/cEdt_name"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="请输入姓名" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginLeft="10dp"

android:layout_marginRight="10dp"

android:orientation="horizontal" >

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="年龄："

android:textSize="23sp" />

<EditText

android:id="@+id/cEdt_age"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="请输入年龄"

android:numeric="integer" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginLeft="10dp"

android:layout_marginRight="10dp"

android:layout_marginTop="10dp"

android:orientation="horizontal" >

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="身高："

android:textSize="23sp" />

<EditText

android:id="@+id/cEdt_height"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="请输入身高"

android:numeric="decimal" />

</LinearLayout>

这个Demo还是很简单的，我就不做过多的解释了。各位看了之后，有什么见解欢迎留言交流交流共同进步。

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