前言

本文参考《Android编程权威指南》第三版。
仅供学习。如有不当之处，还望指正。

1. string.html

<resources>
    <string name="app_name">CriminalIntent</string>
<!--    添加字符串资源-->
    <string name="crime_title_hint">Enter a title for the crime.</string>
    <string name="crime_title_label">Title</string>
    <string name="crime_details_label">Details</string>
    <string name="crime_solved_label">Solved</string>
</resources>

2. activity_crime.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

3. fragment_crime.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    android:layout_margin="16dp"

    <!--    fragment视图的布局文件-->
    <TextView
        style="?android:listSeparatorTextViewStyle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/crime_title_label"/>
    <EditText
        android:id="@+id/crime_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/crime_title_hint"/>
    <TextView
        style="?android:listSeparatorTextViewStyle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/crime_details_label"/>
    <Button
        android:id="@+id/crime_date"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <CheckBox
        android:id="@+id/crime_solved"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/crime_solved_label"/>
</LinearLayout>

4. MainActivity.java

package com.example.criminalintent;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_crime);


        FragmentManager fm = getSupportFragmentManager();//获取FragmentManager

//        添加一个CrimeFragment
        Fragment fragment = fm.findFragmentById(R.id.fragment_container);
        if (fragment == null){
            fragment = new CrimeFragment();
            fm.beginTransaction().add(R.id.fragment_container,fragment).commit();
        }
    }
}

5.CrimeFragment.java

package com.example.criminalintent;

import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;
import android.widget.RadioGroup;

import androidx.fragment.app.Fragment;

public class CrimeFragment extends Fragment { //继承Fragment类

//    覆盖Fragment.onCreate(Bundle)方法
    private Crime mCrime;
    private EditText mTitleField;
    private Button mDateButton;
    private CheckBox mSolvedCheckBox;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mCrime = new Crime();
    }
//    覆盖onCreateView(...)方法
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceSate) {
        View v = inflater.inflate(R.layout.fragment_crime,container,false);

        mTitleField = (EditText)v.findViewById(R.id.crime_title);
        mTitleField.addTextChangedListener(new TextWatcher(){
            @Override
            public void beforeTextChanged(
                    CharSequence s,int start,int count,int after) {
                // This space intentionally left blank
            }

            @Override
            public void onTextChanged(
                    CharSequence s, int start, int before, int count) {
                mCrime.setTitle(s.toString());
            }

            @Override
            public void afterTextChanged(Editable s) {
                // This one too
            }
        });
//        设置Button文字
        mDateButton = (Button)v.findViewById(R.id.crime_date);
        mDateButton.setText(mCrime.getDate().toString());
        mDateButton.setEnabled(false);

//        监听CheckBox的变化
        mSolvedCheckBox = (CheckBox)v.findViewById(R.id.crime_solved);

        mSolvedCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView,
                                         boolean isChecked) {
                mCrime.setSolved(isChecked);
            }
        });
        return v;
    }

}

6. Crime.java

package com.example.criminalintent;

import java.util.Date;
import java.util.UUID;

public class Crime {

//    Crime类的新增代码
    private UUID mId;
    private String mTitle;
    private Date mDate;
    private boolean mSolved;

    Crime(){
        mId = UUID.randomUUID();//调用UUID.randomUUID()产生一个随机唯一ID值
        mDate = new Date();
    }

    public UUID getId() {
        return mId;
    }

    public String getTitle() {
        return mTitle;
    }

    public void setTitle(String title) {
        mTitle = title;
    }

    public Date getDate() {
        return mDate;
    }

    public void setDate(Date date) {
        mDate = date;
    }

    public boolean isSolved() {
        return mSolved;
    }

    public void setSolved(boolean solved) {
        mSolved = solved;
    }
}