android入门小Demo

分享一个android端的小例子，代码虽少，五脏俱全。

得到的效果是

废话不多说，直接上代码。

我们先看项目的结构。

我们的主活动页面是activity_main.xml   代码如下

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

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


    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical|center_horizontal"
        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>

    <Button
        android:id="@+id/cheat_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|center"
        android:text="@string/cheat_button"/>

    <Button
        android:id="@+id/next_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:text="@string/next_button"/>


</FrameLayout>

对应的活动页面是MainActivity.java，代码如下：

package ligz.com.geoquiz;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "QuizActivity";
    private static final String KEY_INDEX = "index";

    private Button mTrueButton;
    private Button mFalseButton;
    private Button mNextButton;
    private TextView mQuestionTextView;
    private Button mCheatButtton;//作弊的按钮
    private boolean mIsCheater;

    private TrueFalse[] mQuestionBank = new TrueFalse[]{
            new TrueFalse(R.string.question_text,true),
            new TrueFalse(R.string.question_text1,true),
            new TrueFalse(R.string.question_text2,true),
            new TrueFalse(R.string.question_text3,true),
            new TrueFalse(R.string.question_text4,false),
    };

    private int mCurrentIndex = 0;

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

    private void checkAnswer(boolean userPressedTrue){
        boolean answerIsTrue = mQuestionBank[mCurrentIndex].ismTrueQuestion();

        int messageResId = 0;

        if(mIsCheater){
            messageResId = R.string.judgment_toast;
        }else{
            if(userPressedTrue == answerIsTrue){
                messageResId = R.string.correct_toast;
            }else{
                messageResId = R.string.incorrect_toast;
            }
        }


        Toast.makeText(this,messageResId,Toast.LENGTH_SHORT).show();
    }


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate(Bundel) called");
        setContentView(R.layout.activity_main);

        //从数组中拿出问题放入TextView
        mQuestionTextView = (TextView)findViewById(R.id.question_text_view);


        /**
         * 正确按钮
         */
        mTrueButton = (Button)findViewById(R.id.true_button);
        //使用监听器
        mTrueButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                checkAnswer(true);
            }
        });
        /**
         * 错误按钮
         */
        mFalseButton = (Button) findViewById(R.id.false_button);
        mFalseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                checkAnswer(false);
            }
        });
        /**
         * 下一道题目按钮
         */
        mNextButton = (Button)findViewById(R.id.next_button);
        mNextButton.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view) {
                mCurrentIndex = (mCurrentIndex + 1) % mQuestionBank.length;
                mIsCheater = false;
                updateQuestion();
            }
        });
        if(savedInstanceState != null){
            mCurrentIndex = savedInstanceState.getInt(KEY_INDEX, 0);
        }
        /**
         * 作弊的按钮跳转
         */
        mCheatButtton = (Button) findViewById(R.id.cheat_button);
        mCheatButtton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //Start CheatActivity
                //跳转activity
                Intent i = new Intent(MainActivity.this, CheatActivity.class);
                //传递内容
                boolean answerIsTrue = mQuestionBank[mCurrentIndex].ismTrueQuestion();
                i.putExtra(CheatActivity.EXTRA_ANSWER_IS_TRUE, answerIsTrue);
                //startActivity(i);
                startActivityForResult(i,0);//第二个参数是请求代码，当一个activity有多个子activity时，且需要区分消息反馈
            }
        });

        updateQuestion();


    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState){//记住当前的答案，当屏幕旋转时，仍可以回到当前问题
        super.onSaveInstanceState(savedInstanceState);
        Log.i(TAG, "onSavedInstanceState");
        savedInstanceState.putInt(KEY_INDEX, mCurrentIndex);
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data){//
        if(data == null){
            return;
        }
        mIsCheater = data.getBooleanExtra(CheatActivity.EXTRA_ANSWER_SHOWN, false);
    }
}

点击cheat按钮，进入查看答案的页面，对应的xml文件是activity_cheat.xml如下：

<?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:orientation="vertical"
    android:gravity="center">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="24dp"
        android:text="@string/warning_text"/>

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

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

对应的CheatActivity.java文件如下：

package ligz.com.geoquiz;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

/**
 * Created by Es muss sein on 2018/9/4.
 */

public class CheatActivity extends Activity{
    public static final String EXTRA_ANSWER_IS_TRUE = "ligz.com.geoquiz.answer_is_true";
    public static final String EXTRA_ANSWER_SHOWN = "ligz.com.geoquiz.answer_show";

    private boolean mAnswerIsTrue;

    private TextView mAnswerTextView;

    private Button mShowAnswer;



    private void setAnswerShowResult(boolean isAnswerShown){
        Intent data = new Intent();
        data.putExtra(EXTRA_ANSWER_SHOWN, isAnswerShown);
        setResult(RESULT_OK, data);
    }

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

        mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false);

        mAnswerTextView = (TextView)findViewById(R.id.answerTextView);

        //答案不会显示除非用户按下按钮
        setAnswerShowResult(false);
        mShowAnswer = (Button)findViewById(R.id.showAnswerButton);
        mShowAnswer.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(mAnswerIsTrue){
                    mAnswerTextView.setText(R.string.true_button);
                }else{
                    mAnswerTextView.setText(R.string.false_button);
                }
                setAnswerShowResult(true);
            }
        });
    }


}

model文件TrueFalse.java如下：

package ligz.com.geoquiz;

/**
 * Created by Es muss sein on 2018/9/3.
 */

public class TrueFalse {
    private int mQuestion;

    private boolean mTrueQuestion;

    public TrueFalse(int mQuestion, boolean mTrueQuestion){
        this.mQuestion = mQuestion;
        this.mTrueQuestion = mTrueQuestion;
    }

    public int getmQuestion() {
        return mQuestion;
    }

    public void setmQuestion(int mQuestion) {
        this.mQuestion = mQuestion;
    }

    public boolean ismTrueQuestion() {
        return mTrueQuestion;
    }

    public void setmTrueQuestion(boolean mTrueQuestion) {
        this.mTrueQuestion = mTrueQuestion;
    }
}

对应Strings.xml如下：

<resources>
    <string name="app_name">GeoQuiz</string>
    <string name="question_text">中国哲学简史的作者是否是冯友兰</string>
    <string name="question_text1">1984的作者是乔治奥威尔吗</string>
    <string name="question_text2">王小波写过沉默的大多数吗</string>
    <string name="question_text3">意志和表象的世界是叔本华的作品吗</string>
    <string name="question_text4">牛棚杂忆和动物庄园的作者是同一人吗</string>

    <string name="cheat_button">cheat!</string>
    <string name="warning_text">你确定要查看答案吗</string>
    <string name="show_answer_button">查看答案</string>
    <string name="judgment_toast">Cheating is wrong</string>

    <string name="true_button">对</string>
    <string name="false_button">错</string>
    <string name="menu_settings">Settings</string>
    <string name="correct_toast">回答正确</string>
    <string name="incorrect_toast">回答错误</string>
    <string name="next_button">下一题</string>
</resources>

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