Criminallntent项目的迭代
Criminallntent项目的迭代
一.Fragment间的数据传递
传递crime的日期给Fragment,需新建一个newInstance(Date)方法，然后将Date作为argument附件给Fragment。为了返回新的日期给Fragment并更新模型层以及对应的视图，需要将日期打包为extra并附加到Intent上，然后调用Fragment.onActivityResult(...)的方法，并传入准备好的Intent参数。
1.添加newInstance()方法（CrimeFragment.java）
@Override
public View onCreateView(LayoutInflater inflater,ViewGroup container,
Bundle savedInstanceState) {
//加载布局
View v=inflater.inflate(R.layout.fragment_main,container,false);
//生成并使用组件
mDateButton=(Button)v.findViewById(R.id.crime_data);
mDateButton.setText(mCrime.getDate().toString());
//mDateButton.setEnabled(false);
mDateButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
FragmentManager manager=getFragmentManager();
//newInstance替换构造方法
//DatePickerFragment dialog=new DatePickerFragment();
DatePickerFragment dialog=DatePickerFragment.newInstance(mCrime.getDate());
//设置目标fragment
dialog.setTargetFragment(MainFragment.this,REQUEST_DATE);
dialog.show(manager,DIALOG_DATE); //显示DialogFragment
}
});
return v;
}
2.传递数据给DatePickerFragment
直接获取保存在arguments中的数据，并将数据显示，最后设置目标fragment。
package com.example.mytest;
import android.app.Activity;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.support.v7.app.AlertDialog;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.DatePicker;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
public class DatePickerFragment extends DialogFragment{
private static final String ARG_DATE="date";
public static final String EXTRA_DATE= "com.example.mytest.date";
private DatePicker mDatePicker;
//便于被调用传递数据给DatePickerFragment
//保存日期到argument bundle中，便于DatePickerFragment直接获取
public static DatePickerFragment newInstance(Date date){
Bundle args=new Bundle();
args.putSerializable(ARG_DATE,date);
DatePickerFragment fragment=new DatePickerFragment();
fragment.setArguments(args);
return fragment;
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
//获取Date对象并初始化DatePicker
Date date=(Date)getArguments().getSerializable(ARG_DATE);
Calendar calendar=Calendar.getInstance();
calendar.setTime(date);
int year=calendar.get(Calendar.YEAR);
int month=calendar.get(Calendar.MONTH);
int day=calendar.get(Calendar.DAY_OF_MONTH);
//添加DatePicker
View v=LayoutInflater.from(getActivity())
.inflate(R.layout.dialog_date,null);
mDatePicker=(DatePicker)v.findViewById(R.id.dialog_date_picker);
mDatePicker.init(year,month,day,null);
return new AlertDialog.Builder(getActivity())
.setView(v)
.setTitle(R.string.date_picker_title)
.setPositiveButton(android.R.string.ok,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
int year=mDatePicker.getYear();
int month=mDatePicker.getMonth();
int day=mDatePicker.getDayOfMonth();
Date date=new GregorianCalendar(year,month,day).getTime();
sendResult(Activity.RESULT_OK,date);
}
})
.create();
}
//回调目标fragment
private void sendResult(int resultCode,Date date){
if (getTargetFragment()==null){
return;
}
Intent intent=new Intent();
intent.putExtra(EXTRA_DATE,date);
getTargetFragment().onActivityResult(getTargetRequestCode(),resultCode,intent);
}
}
3.托管MainFragment，使界面呈现出来。(MainActivity.java)
package com.example.mytest;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FragmentManager fm=getSupportFragmentManager();
Fragment fragment=fm.findFragmentById(R.id.fragment_container);
if (fragment==null){
fragment=new MainFragment();
fm.beginTransaction()
.add(R.id.fragment_container,fragment)
.commit();
}
}
}
二.SQlite数据库
SQLite是类似于MySQL和Postgresql的开源关系型数据库。不同于其他数据库的是，SQLite使用单个文件存储数据，使用SQLite库读取数据。
Android标准库包含SQLite库以及配套的一些Java辅助类。
1.定义 CrimeTable 内部类（CrimeDbSchema.java）
public class CrimeDbSchema {
public static final class CrimeTable {
public static final String NAME = "crimes";
}
}
2.定义数据表字段（CrimeDbSchema.java）
public static final class Cols {
public static final String UUID = "uuid";
public static final String TITLE = "title";
public static final String DATE = "date";
public static final String SOLVED = "solved";
}
3.创建 CrimeBaseHelper 类（CrimeBaseHelper.java）
public class CrimeBaseHelper extends SQLiteOpenHelper {
private static final int VERSION = 1;
private static final String DATABASE_NAME = "crimeBase.db";
public CrimeBaseHelper(Context context) {
super(context, DATABASE_NAME, null, VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
4.打开 SQLiteDatabase （CrimeLab.java）
public class CrimeLab {
private static CrimeLab sCrimeLab;
private List<Crime> mCrimes;
private Context mContext;
private SQLiteDatabase mDatabase;
...
private CrimeLab(Context context) {
mContext = context.getApplicationContext();
mDatabase = new CrimeBaseHelper(mContext)
.getWritableDatabase();
mCrimes = new ArrayList<>();
}
5.创建crime表（CrimeBaseHelper.java）
db.execSQL("create table " + CrimeTable.NAME + "(" +
" _id integer primary key autoincrement, " +
CrimeTable.Cols.UUID + ", " +
CrimeTable.Cols.TITLE + ", " +
CrimeTable.Cols.DATE + ", " +
CrimeTable.Cols.SOLVED +
")"
);
6.写入数据库的语法
创建一个数据表
CREATE TABLE table_name(
column1 datatype,
column2 datatype,
column3 datatype,
.....
columnN datatype,
PRIMARY KEY( one or more columns )
);
创建一个索引
CREATE UNIQUE INDEX index_name
ON table_name ( column1, column2,...columnN);
插入一条记录
INSERT INTO tablename VALUES(?,?,?)
SELECT * FROM tablename;
更改一条记录
UPDATE tablename SET column1='newname';
SELECT * FROM Teachers;
根据字段删除一条记录
DELETE FROM tablename WHERE id='1';
SELECT * FROM tablename;
