轉載請注明出處https://blog.csdn.net/m0_50043719/article/details/120481526

前言

本文參考《Android編程權威指南》第三版，
僅供學習，侵權即刪，
如有不當之處,還望指正，
本博客是在上一篇的基礎上進行修改的，
這是上一篇博客鏈接：Android編程權威指南第3版 2.8 挑戰練習：添加后退按鈕

1. 題目描述

如果前進與后退按鈕上只顯示指示圖示，用戶界面更清爽，如下圖：

要完成此練習，需將普通的Button組件替換成ImageButton組件，
ImageButton組件繼承自ImageView，Button組件則繼承自TextView，ImageButton和
Button與View間的繼承關系如圖所示

2. MainActivity.java

package com.example.test3;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button mTrueButton;
    private Button mFalseButton;
    private ImageButton mPrevButton;//修改這里
    private ImageButton mNextButton;//修改這里
    private TextView mQuestionTextView;



    private Question[] mQuestionBank = new Question[] {
            new Question(R.string.question_australia, true),
            new Question(R.string.question_oceans, true),
            new Question(R.string.question_mideast, false),
            new Question(R.string.question_africa, false),
            new Question(R.string.question_americas, true),
            new Question(R.string.question_asia, true)
    };

    private int mCurrentIndex = 0;

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

        mQuestionTextView = (TextView) findViewById(R.id.question_text_view);
//        為 TextView 添加監聽器
        mQuestionTextView.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view) {
                mCurrentIndex = (mCurrentIndex + 1) % mQuestionBank.length;
                updateQuestion();
            }
        });
        updateQuestion();
        mTrueButton = (Button) findViewById(R.id.true_button);
        mTrueButton.setOnClickListener(new View.OnClickListener(){
            @Override
            public  void onClick(View v){
                checkAnswer(true);//呼叫checkAnswer(boolean)方法
            }
        });

        mFalseButton =(Button) findViewById(R.id.false_button);
        mFalseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v){
                checkAnswer(false);//呼叫checkAnswer(boolean)方法
            }
        });

        mPrevButton = (ImageButton) findViewById(R.id.prev_button);//這里也需要修改
        mPrevButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mCurrentIndex = (mCurrentIndex - 1 + mQuestionBank.length) % mQuestionBank.length;

                updateQuestion();
            }
        });
        updateQuestion();

        mNextButton = (ImageButton) findViewById(R.id.next_button);//還有
        mNextButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mCurrentIndex = (mCurrentIndex + 1) %  mQuestionBank.length;
                updateQuestion();

            }
        });
        updateQuestion();

    }
    private void updateQuestion() {
        int question = mQuestionBank[mCurrentIndex].getTextRestId();
        mQuestionTextView.setText(question);

    }
//    增加checkAnswer(boolean)方法
    private void checkAnswer(boolean userPressedTrue) {
        boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswerTrue();

        int messageResId = 0;

        if(userPressedTrue == answerIsTrue) {
            messageResId = R.string.correct_toast;
        }else{
            messageResId = R.string.incorrect_toast;
        }
        Toast.makeText(this,messageResId,Toast.LENGTH_SHORT).show();
    }

}

3. Question.java

package com.example.test3;

public class Question {
    private int mTextRestId;//變數mTextResId用來保存地理知識,而問題字串的資源ID，資源ID總是int型別，所以這里設定它為int型別，
    private boolean mAnswerTrue;

    public Question(int textRestId, boolean answerTrue) {
        mTextRestId = textRestId;
        mAnswerTrue = answerTrue;
    }

    public int getTextRestId() {
        return mTextRestId;
    }

    public void setTextRestId(int textRestId) {
        mTextRestId = textRestId;
    }

    public boolean isAnswerTrue() {
        return mAnswerTrue;
    }

    public void setAnswerTrue(boolean answerTrue) {
        mAnswerTrue = answerTrue;
    }
}

4. activity_main.xml

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

    <TextView
        android:id="@+id/question_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="24dp"  />

    <LinearLayout

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/true_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/true_button" />

        <Button
            android:id="@+id/false_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/false_button" />

    </LinearLayout>

    <LinearLayout

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

<!--        需要修改以下兩個位置-->
         <ImageButton
            android:id="@+id/prev_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/arrow_left" />


         <ImageButton
            android:id="@+id/next_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
           android:src="@drawable/arrow_right" />

    </LinearLayout>

</LinearLayout>

5. strings.xml

<resources>
    <string name="app_name">test3</string>
    <string name="question_australia">Canberra is the capital of Australia.</string>
    <string name="question_oceans">The Pacific Ocean is larger than the Atlantic Ocean.</string>
    <string name="question_mideast">The Suez Canal connects the Red Sea and the Indian Ocean.</string>
    <string name="question_africa">The source of the Nile River is in Egypt.</string>
    <string name="question_americas">The Amazon River is the longest river in the Americas.</string>
    <string name="question_asia">Lake Baikal is the world\'s oldest and deepest freshwater lake.</string>//為得到符號'，這里使用了轉義字符，
    <string name="true_button">True</string>
    <string name="false_button">False</string>
    <string name="next_button">Next</string><!--    添加新按鈕所需的字串資源定義-->
    <string name="prev_button">Prev</string><!--    prev按鈕-->
    <string name="correct_toast">Correct!</string>
    <string name="incorrect_toast">Incorrect!</string>
</resources>

6. 效果