android studio三张图片切换的详细代码

以下是基于ViewPager实现的三张图片切换的详细代码：

1. 在布局文件中定义ViewPager和指示器：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <LinearLayout
        android:id="@+id/indicatorLayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:orientation="horizontal" />

</RelativeLayout>

2. 创建一个adapter来显示图片：

public class ImagePagerAdapter extends PagerAdapter {
    private Context mContext;
    private int[] mImageIds;

    public ImagePagerAdapter(Context context, int[] imageIds) {
        mContext = context;
        mImageIds = imageIds;
    }

    @Override
    public int getCount() {
        return mImageIds.length;
    }

    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return view == object;
    }

    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        ImageView imageView = new ImageView(mContext);
        imageView.setImageResource(mImageIds[position]);
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        container.addView(imageView);
        return imageView;
    }

    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        container.removeView((ImageView) object);
    }
}

3. 在Activity中初始化ViewPager和指示器：

public class MainActivity extends AppCompatActivity {
    private ViewPager mViewPager;
    private LinearLayout mIndicatorLayout;
    private int[] mImageIds = {R.drawable.image1, R.drawable.image2, R.drawable.image3};

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

        mViewPager = findViewById(R.id.viewPager);
        mIndicatorLayout = findViewById(R.id.indicatorLayout);

        ImagePagerAdapter adapter = new ImagePagerAdapter(this, mImageIds);
        mViewPager.setAdapter(adapter);

        addIndicators();
        setCurrentIndicator(0);

        mViewPager.addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                setCurrentIndicator(position);
            }
        });
    }

    private void addIndicators() {
        for (int i = 0; i < mImageIds.length; i++) {
            ImageView imageView = new ImageView(this);
            LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.WRAP_CONTENT,
                    LinearLayout.LayoutParams.WRAP_CONTENT);
            lp.setMargins(10, 0, 10, 0);
            imageView.setLayoutParams(lp);
            imageView.setImageResource(R.drawable.indicator_selector);
            mIndicatorLayout.addView(imageView);
        }
    }

    private void setCurrentIndicator(int position) {
        for (int i = 0; i < mImageIds.length; i++) {
            ImageView imageView = (ImageView) mIndicatorLayout.getChildAt(i);
            if (i == position) {
                imageView.setSelected(true);
            } else {
                imageView.setSelected(false);
            }
        }
    }
}

4. 创建一个indicator_selector.xml文件来定义指示器的选中和未选中状态：

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/indicator_selected" android:state_selected="true" />
    <item android:drawable="@drawable/indicator_unselected" />
</selector>

5. 在drawable文件夹中创建indicator_selected.png和indicator_unselected.png两张图片，用于指示器的选中和未选中状态。

注意：以上代码中的图片资源需要根据实际情况进行更改。