android|Android编程权威指南第3版 2.9 挑战练习（从按钮到图标按钮） android|android

转载请注明出处https://blog.csdn.net/m0_50043719/article/details/120481526

目录

前言
1. 题目描述
2. MainActivity.java
3. Question.java
4. activity_main.xml
5. strings.xml
6. 效果

前言本文参考《Android编程权威指南》第三版。
仅供学习，侵权即删。
如有不当之处,还望指正。
本博客是在上一篇的基础上进行修改的。
这是上一篇博客链接：Android编程权威指南第3版 2.8 挑战练习：添加后退按钮
1. 题目描述如果前进与后退按钮上只显示指示图标，用户界面更清爽，如下图：

android|Android编程权威指南第3版 2.9 挑战练习（从按钮到图标按钮）

文章图片

要完成此练习，需将普通的Button组件替换成ImageButton组件。
ImageButton组件继承自ImageView。Button组件则继承自TextView。ImageButton和
Button与View间的继承关系如图所示

文章图片

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; //修改这里 private ImageButton mNextButton; //修改这里 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); //为 TextView 添加监听器 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 publicvoid onClick(View v){checkAnswer(true); //调用checkAnswer(boolean)方法 } }); mFalseButton =(Button) findViewById(R.id.false_button); mFalseButton.setOnClickListener(new View.OnClickListener() {@Override public void onClick(View v){checkAnswer(false); //调用checkAnswer(boolean)方法 } }); mPrevButton = (ImageButton) findViewById(R.id.prev_button); //这里也需要修改 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); //还有 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; //变量mTextResId用来保存地理知识,而问题字符串的资源ID。资源ID总是int类型，所以这里设置它为int类型。 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

5. strings.xml

="app_name">test3 ="question_australia">Canberra is the capital of Australia. ="question_oceans">The Pacific Ocean is larger than the Atlantic Ocean. ="question_mideast">The Suez Canal connects the Red Sea and the Indian Ocean. ="question_africa">The source of the Nile River is in Egypt. ="question_americas">The Amazon River is the longest river in the Americas. ="question_asia">Lake Baikal is the world\'s oldest and deepest freshwater lake.//为得到符号'，这里使用了转义字符。 ="true_button">True ="false_button">False ="next_button">Next ="prev_button">Prev ="correct_toast">Correct! ="incorrect_toast">Incorrect!

6. 效果 【android|Android编程权威指南第3版 2.9 挑战练习（从按钮到图标按钮）】