Android(2_5)作业之我的家乡图册

图片的切换：第一张图片的上一张切换到最后一张图片，同样，最后一张图片的下一站切换到第一张图片。（用取模%运算实现）

代码如下

MainActivity.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    ImageView img;
    Button btn_last,btn_next;
    TextView txt;
    private int[] imgs={
            R.drawable.img1,
            R.drawable.img2,
            R.drawable.img3,
            R.drawable.img4,
            R.drawable.img5,
            R.drawable.img6,
    };
    int index=0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        img=(ImageView)findViewById(R.id.img);
        txt=(TextView)findViewById(R.id.text);
        btn_last=(Button)findViewById(R.id.btn_last);
        btn_next=(Button)findViewById(R.id.btn_next);
        btn_last.setOnClickListener(new mclick());
        btn_next.setOnClickListener(new mclick());
    }
    class mclick implements OnClickListener{
        @Override
        public void onClick(View v) {
            if (v==btn_last){
                if (index<=0) index=6;
                    index--;
                    img.setImageResource(imgs[index]);
                    txt.setText("图片"+(index+1));

            }
            if (v==btn_next){
                index++;
                index=index%imgs.length;
                img.setImageResource(imgs[index]);
                txt.setText("图片"+(index+1));
            }
        }
    }
}

activity_main.xml

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

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center">
        <ImageView
            android:id="@+id/img"
            android:layout_width="240dip"
            android:layout_height="240dip"
            android:layout_centerVertical="true"
            android:src="@drawable/img1"
            />

    </LinearLayout>
        <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:layout_gravity="center"
            android:text="@string/name"/>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/btn_last"
            android:layout_width="150dip"
            android:layout_height="wrap_content"
            android:text="上一张"
            />
        <Button
            android:id="@+id/btn_next"
            android:layout_width="150dip"
            android:layout_height="wrap_content"
            android:text="下一张"
            />
    </LinearLayout>

</LinearLayout>

strings.xml

<resources>
    <string name="app_name">ex2_13</string>
    <string name="name">我的家乡</string>
</resources>