Android Gallery 的 getView() 返回不正确的位置

Question

感谢阅读!

我使用 Android Gallery 将 LayoutParams 作为 MATCH_PARENT 一次显示一个全屏图像。

这是我的代码:

布局.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" android:layout_height="fill_parent">
    <Gallery
        android:id="@+id/gallery" android:layout_width="fill_parent"
        android:layout_height="fill_parent">
    </Gallery>
    <TextView android:id="@+id/tvShowText" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:layout_alignParentBottom="true" />
</RelativeLayout>

HelloGallery.java

package com.android.sagar;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class HelloGallery extends Activity {

    TextView tvShowText = null;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        tvShowText = (TextView)findViewById(R.id.tvShowText);

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

        g.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView parent, View v, int position, long id) {
                Toast.makeText(HelloGallery.this, "" + position, Toast.LENGTH_SHORT).show();
            }
        });
    }

    public class ImageAdapter extends BaseAdapter {
        int mGalleryItemBackground;
        private Context mContext;

        private Integer[] mImageIds = {
                R.drawable.pic1,
                R.drawable.pic2,
                R.drawable.pic3
        };

        public ImageAdapter(Context c) {
            mContext = c;
        }

        public int getCount() {
            return mImageIds.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);

            tvShowText.setText("ImageCaption for Image No.: "+position);

            i.setImageResource(mImageIds[position]);
            i.setLayoutParams(new Gallery.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
            i.setScaleType(ImageView.ScaleType.FIT_XY);
            i.setBackgroundResource(mGalleryItemBackground);

            return i;
        }
    }
}

图像显示正确，但我打印的标题有一个偏差，有时甚至完全不同。 :(

我调试后发现，当我滑动一次时，getView() 会被调用多次——大约 2 到 3 次……它们都在不同的位置，但图像似乎一次移动一个。 :(请帮忙!

Answer 1

为了正确更新您的标题，您需要覆盖Gallery 的OnItemSelectedListener。 Sujit 在他的评论中是正确的，调用 getView 是为了渲染(或在某些情况下预渲染或后渲染)Gallery 中的每个图像。不应依赖于它来识别选择了哪个图像。相反，在 HelloGallery onCreate() 方法中覆盖 OnItemSelectedListener:

    g.setOnItemSelectedListener(new OnItemSelectedListener() 
    {
       @Override
       public void onItemSelected(AdapterView<?> parent, View view, int position, long id) 
       {
          tvShowText.setText("ImageCaption for Image No.: "+position);
       }
       @Override
       public void onNothingSelected(AdapterView<?> arg0) 
       {
          tvShowText.setText("No image selected");
       }
    });