4解决图片乱跳的问题,preferenceactivity.

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listview中图片异步加载时，图片乱跳错位的现象
原因：这是由于在代码中复用了convertview，同时也复用了convertview中的bitmap，
解决：
①不用convertview缓存，但程序的效率打折扣
②可以用convertview缓存，在xml中不配置ImageView，在代码中手动添加
③自定义一个ImageView，同时具有异步加载的功能

<?xml version="1.0" encoding="UTF-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:id="@+id/list_item_layout"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:background="@drawable/category_selector"

    android:gravity="center_vertical"

    android:orientation="vertical" >

    <LinearLayout

        android:layout_width="fill_parent"

        android:layout_height="fill_parent"

        android:orientation="horizontal" >

        <LinearLayout

            android:id="@+id/ll_book_image"

            android:layout_width="wrap_content"

            android:layout_height="fill_parent"

            android:orientation="vertical" >

            <RatingBar

                android:id="@+id/ratingbar"

                style="?android:attr/ratingBarStyleSmall"

                android:layout_width="65.0dip"

                android:layout_height="wrap_content"

                android:layout_gravity="center_vertical"

                android:isIndicator="true"

                android:numStars="5"

                android:paddingTop="3dip"

                android:stepSize="0.5" />

        </LinearLayout>

        <LinearLayout

            android:layout_width="fill_parent"

            android:layout_height="fill_parent"

            android:orientation="vertical"

            android:paddingLeft="15dip" >

            <TextView

                android:id="@+id/book_title"

                android:layout_width="wrap_content"

                android:layout_height="wrap_content"

                android:maxHeight="50dip"

                android:textColor="@android:color/black"

                android:textSize="20dp"

                android:textStyle="bold" />

            <TextView

                android:id="@+id/book_description"

                android:layout_width="wrap_content"

                android:layout_height="wrap_content"

                android:maxHeight="60dip"

                android:textColor="@android:color/black"

                android:textSize="15dp" />

        </LinearLayout>

    </LinearLayout>

</LinearLayout>  
考虑如果不设置ratingbar样式有影响吗？

        public View getView(int position, View convertView, ViewGroup parent) {

            NewBook newbook = newbooks.get(position);

            View view;

            if (convertView == null) {

                view = View.inflate(NewBookActivity.this,

                        R.layout.new_book_item, null);

            } else {

                view = convertView;

            }

            final ImageView iv = new ImageView(NewBookActivity.this);

            // RatingBar rb = new RatingBar(NewBookActivity.this);

            RatingBar rb = new RatingBar(NewBookActivity.this, null,

                    android.R.attr.ratingBarStyleSmall);

            rb.setMax(5);

            rb.setProgress(4);

            LinearLayout ll = (LinearLayout) view

                    .findViewById(R.id.ll_book_image);

            // 清空ll的里面的view对象

            ll.removeAllViews();

            ll.addView(iv, new LayoutParams(60, 60));

            ll.addView(rb, new LayoutParams(60, LayoutParams.WRAP_CONTENT));

            TextView tv_title = (TextView) view.findViewById(R.id.book_title);

            TextView tv_description = (TextView) view

                    .findViewById(R.id.book_description);

            rb.setRating(4.0f);

            tv_title.setText(newbook.getName());

            tv_description.setText(newbook.getDescription());

            SharedPreferences sp = PreferenceManager

                    .getDefaultSharedPreferences(getApplicationContext());

            boolean canloadicon = sp.getBoolean("canloadicon", false);

            if (canloadicon) {

                LoadImageAsynTask task = new LoadImageAsynTask(

                        new LoadImageAsynTaskCallback() {

                            public void beforeLoadImage() {

                                iv.setImageResource(R.drawable.book);

                            }

                            public void afterLoadImage(Bitmap bitmap) {

                                if (bitmap != null) {

                                    iv.setImageBitmap(bitmap);

                                } else {

                                    iv.setImageResource(R.drawable.book);

                                }

                            }

                        });

                task.execute(newbook.getIconpath());

            } else {

                iv.setImageResource(R.drawable.book);

            }

            return view;

        }

    }  

SharedpreferenceActivity
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