我正在为我的应用程序创建一个简单的ViewPager库。这是我迄今为止实现的代码。
这是我的xml文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.newgallery.MainActivity" >
<android.support.v4.view.ViewPager
android:id="@+id/view_pager"
android:layout_width="match_parent"
android:layout_height="240dp" />
</LinearLayout>
这是我的java文件
public class MainActivity extends Activity {
private Bitmap[] IMAGES;
Bitmap bit1,bit2,bit3,bit4;
String getid, url1,url2,url3,url4;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getid = "14";
url1 = "http://example.com/dom/uploads/"+getid+"/img1.jpg";
url2 = "http://example.com/dom/uploads/"+getid+"/img2.jpg";
url3 = "http://example.com/dom/uploads/"+getid+"/img3.jpg";
url4 = "http://example.com/dom/uploads/"+getid+"/img4.jpg";
bit1 = LoadImages(url1);
bit2 = LoadImages(url2);
bit3 = LoadImages(url3);
bit4 = LoadImages(url4);
IMAGES = new Bitmap[]{bit1,bit2,bit3,bit4};
ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
ImageAdapter adapter = new ImageAdapter();
viewPager.setAdapter(adapter);
}
class ImageAdapter extends PagerAdapter {
@Override
public int getCount() {
return IMAGES.length;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == ((ImageView) object);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView imageView = new ImageView(getApplicationContext());
imageView.setImageBitmap(IMAGES[position]);
((ViewPager) container).addView(imageView, 0);
return imageView;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((ImageView) object);
}
}
Bitmap result;
public Bitmap LoadImages(String url){
ImageLoader imageLoader = AppController.getInstance().getImageLoader();
imageLoader.get(url, new ImageListener() {
@Override
public void onErrorResponse(VolleyError error) {
Bitmap drawimg = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
result = drawimg;
}
@Override
public void onResponse(ImageContainer response, boolean arg1) {
if (response.getBitmap() != null) {
result = response.getBitmap();
}
}
});
return result;
}
}
这是我的Logcat。
所有链接都正常工作。在这里,我将原始域更改为example.com
09-02 19:36:35.568: D/Volley(630): [76] BasicNetwork.logSlowRequests: HTTP response for request=<[ ] http://example.com/dom/uploads/14/img2.jpg 0x90e75755 LOW 2> [lifetime=3027], [size=107746], [rc=200], [retryCount=0]
09-02 19:36:35.568: D/Volley(630): [74] BasicNetwork.logSlowRequests: HTTP response for request=<[ ] http://example.com/dom/uploads/14/img1.jpg 0x90e75755 LOW 1> [lifetime=3075], [size=89388], [rc=200], [retryCount=0]
09-02 19:36:35.798: D/dalvikvm(630): GC_FOR_ALLOC freed 281K, 4% free 19781K/20487K, paused 84ms, total 85ms
09-02 19:36:35.808: I/dalvikvm-heap(630): Grow heap (frag case) to 20.002MB for 544016-byte allocation
09-02 19:36:35.918: D/dalvikvm(630): GC_FOR_ALLOC freed <1K, 4% free 20312K/21063K, paused 101ms, total 101ms
09-02 19:36:36.028: D/dalvikvm(630): GC_CONCURRENT freed <1K, 4% free 20312K/21063K, paused 30ms+22ms, total 100ms
09-02 19:36:36.108: D/Volley(630): [1] Request.finish: 4019 ms: [ ] http://example.com/dom/uploads/14/img3.jpg 0x90e75755 LOW 3
09-02 19:36:36.218: D/dalvikvm(630): GC_FOR_ALLOC freed 18K, 4% free 20313K/21063K, paused 69ms, total 69ms
09-02 19:36:36.228: I/dalvikvm-heap(630): Grow heap (frag case) to 20.522MB for 544016-byte allocation
09-02 19:36:36.318: D/dalvikvm(630): GC_FOR_ALLOC freed 0K, 4% free 20845K/21639K, paused 84ms, total 84ms
09-02 19:36:36.428: D/dalvikvm(630): GC_CONCURRENT freed 1K, 4% free 20845K/21639K, paused 30ms+9ms, total 98ms
09-02 19:36:36.568: D/Volley(630): [1] Request.finish: 4472 ms: [ ] http://example.com/dom/uploads/14/img4.jpg 0x90e75755 LOW 4
09-02 19:36:36.638: D/dalvikvm(630): GC_FOR_ALLOC freed 20K, 4% free 20845K/21639K, paused 63ms, total 64ms
09-02 19:36:36.648: I/dalvikvm-heap(630): Grow heap (frag case) to 21.041MB for 544016-byte allocation
09-02 19:36:36.728: D/dalvikvm(630): GC_FOR_ALLOC freed 0K, 4% free 21376K/22215K, paused 77ms, total 77ms
09-02 19:36:36.908: D/Volley(630): [1] Request.finish: 4813 ms: [ ] http://example.com/dom/uploads/14/img2.jpg 0x90e75755 LOW 2
09-02 19:36:36.978: D/Volley(630): [1] Request.finish: 4897 ms: [ ] http://example.com/dom/uploads/14/img1.jpg 0x90e75755 LOW 1
所以我的问题是,当我第一次尝试运行我的应用程序时,它不会加载图像。我得到4张白纸。但如果我退出程序并再次运行它,我可以看到所有图像都加载得很好。
之后,我只需按下后退按钮,通过单击启动程序图标再次启动应用程序。
我在这里错过了什么?有人能解释一下原因吗?
