Question

我搜索了显示图片的方法，然后找到了exampple。我想知道为什么imageswitcher被用于imageview？它是否有任何特定的好处？

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

    <ImageSwitcher android:id="@+id/switcher"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
    />

    <Gallery android:id="@+id/gallery"
        android:background="#55000000"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"

        android:gravity="center_vertical"
        android:spacing="16dp"
    />

</RelativeLayout>

Java代码：

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.Gallery.LayoutParams;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ViewSwitcher;

public class ImageGalleryExample extends Activity implements
        AdapterView.OnItemSelectedListener, ViewSwitcher.ViewFactory {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);

        setContentView(R.layout.main);

        mSwitcher = (ImageSwitcher) findViewById(R.id.switcher);
        mSwitcher.setFactory(this);
        mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,
                android.R.anim.fade_in));
        mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,
                android.R.anim.fade_out));

        Gallery g = (Gallery) findViewById(R.id.gallery);
        g.setAdapter(new ImageAdapter(this));
        g.setOnItemSelectedListener(this);
    }

    public void onItemSelected(AdapterView<?> parent, View v, int position, long id) {
        mSwitcher.setImageResource(mImageIds[position]);
    }

    public void onNothingSelected(AdapterView<?> parent) {
    }

    public View makeView() {
        ImageView i = new ImageView(this);
        i.setBackgroundColor(0xFF000000);
        i.setScaleType(ImageView.ScaleType.FIT_CENTER);
        i.setLayoutParams(new ImageSwitcher.LayoutParams(LayoutParams.MATCH_PARENT,
                LayoutParams.MATCH_PARENT));
        return i;
    }

    private ImageSwitcher mSwitcher;

    public class ImageAdapter extends BaseAdapter {
        public ImageAdapter(Context c) {
            mContext = c;
        }

        public int getCount() {
            return mThumbIds.length;
        }

        public Object getItem(int position) {
            return position;
        }

        public long getItemId(int position) {
            return position;
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView i = new ImageView(mContext);

            i.setImageResource(mThumbIds[position]);
            i.setAdjustViewBounds(true);
            i.setLayoutParams(new Gallery.LayoutParams(
                    LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
            i.setBackgroundResource(R.drawable.picture_frame);
            return i;
        }

        private Context mContext;

    }

    private Integer[] mThumbIds = {
            R.drawable.sample_thumb_0, R.drawable.sample_thumb_1,
            R.drawable.sample_thumb_2, R.drawable.sample_thumb_3};

    private Integer[] mImageIds = {
            R.drawable.sample_0, R.drawable.sample_1, R.drawable.sample_2,
            R.drawable.sample_3};

}

Answer 1

如果您想要滑动显示多个图像，可能会带来很多好处。

它给你：

缩放图像以适合屏幕
滑动时轻松控制动画
查看回收以节省内存

如果您认为自己可以做得更好，那么您可以自己完成整个实施。但这需要付出很多努力，这不是非常必要的。

Answer 2

有时您不希望图像突然出现在屏幕上，相反，你想在图像上应用某种动画从一个图像转换到另一个图像。这是由android支持的 ImageSwitcher的形式。

More Details With Sample

图像切换器有什么好处？

2 个答案: