我最近开始为Android设备编程
我正在使用 ViewPager 和碎片（注意：我使用的是v4和v7支持库）
ActionBar （对于标签导航）。
Everythings运行正常，除非我尝试从URL获取到ImageView。
让我解释一下我的所作所为 -
1）我从我的服务器请求一张照片网址
2）我用它来设置imageview位图
Bitmap bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
curlikeimage.setImageBitmap(bmp);
设置图像后，视图不会更新（I.E图像视图仍然是旧图像，没有来自URL的图像）
但是在我切换到另一个标签并返回带有imageview的标签后，图像视图图像会更新！
我尝试使用invalidate（）和postinvalidate（）但没有成功
发生的另一个奇怪的事情是，当我设置图像时（就像之前说过的，使用URL）
然后滑动到第3或第4个选项卡（我有4个选项卡 - tab1 | tab2 | tab3 | tab4，imageview在tab1上）
所有标签都变成空白（I.E它们消失了）
代码 -
MainActivity.java
public class MainActivity extends android.support.v7.app.ActionBarActivity implements
android.support.v7.app.ActionBar.TabListener
{
private ViewPager viewPager;
private vertCollectionPagerAdapter mAdapter;
private ActionBar actionBar;
private String[] tabs = { "tab1", "tab2", "tab3","tab4" };
public void setActionBar()
{
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getSupportActionBar();
FragmentManager fm = getSupportFragmentManager();
mAdapter = new vertCollectionPagerAdapter(fm);
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setBackgroundDrawable(new ColorDrawable(Color.WHITE));
actionBar.setTitle(Html.fromHtml("<font color=\"black\">AppTitle</font>"));
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
@Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setActionBar();
}
public void SignOut()
{
LoginActivity.mApp.resetAccessToken();
Intent i = new Intent(this,LoginActivity.class);
finish();
startActivity(i);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.action_signout:
SignOut();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void onTabReselected(Tab arg0,
android.support.v4.app.FragmentTransaction arg1) {
// TODO Auto-generated method stub
}
@Override
public void onTabSelected(Tab arg0,
android.support.v4.app.FragmentTransaction arg1) {
// TODO Auto-generated method stub
viewPager.setCurrentItem(arg0.getPosition());
}
@Override
public void onTabUnselected(Tab arg0,
android.support.v4.app.FragmentTransaction arg1) {
// TODO Auto-generated method stub
}
}
vertCollectionPagerAdapter.java
public class vertCollectionPagerAdapter extends FragmentPagerAdapter {
private static final int FRAGMENT_COUNT = 4;
private List<Fragment> mFragments = new ArrayList<Fragment>();
// Google's Android MAP API 2 has MapFragment and the Android Support library's equivalent, SupportMapFragment
private FragmentManager mFM;
public boolean disableSwipe = false;
public vertCollectionPagerAdapter(FragmentManager fm) {
super(fm);
mFM = fm;
// add fragments
mFragments.add(new tab1frag());
mFragments.add(new tab2frag());
mFragments.add(new tab3frag());
mFragments.add(new tab4frag());
}
@Override
public int getCount() {
return FRAGMENT_COUNT;
}
// This is called by the ViewPager to get the fragment at tab position pos
// ViewPager calls this when the Tab handler handles a tab change
@Override
public Fragment getItem(int pos) {
Fragment f = mFragments.get(pos);
// we want to disable swiping on the map fragment
disableSwipe = false;
return f;
}
public Fragment getActiveFragment(ViewPager container, int pos) {
String name = "android:switcher:" + container.getId() + ":" + pos;
return mFM.findFragmentByTag(name);
}
}
tab1frag.java
public class tab1frag extends Fragment {
public static String curPic = "";
public View rootView;
public ImageView curlikeimage;
public void getNewPic() {
curPic = "";
Thread thread = new Thread() {
@Override
public void run() {
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(
"http://myserver/getimage");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
// Execute HTTP Post Request
HttpResponse response = httpclient.execute(httppost);
String result = EntityUtils.toString(response.getEntity());
Log.e("hey", result);
if (result.startsWith("OK")) {
response = null;
try {
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet();
String pic2get = result.substring(2);
request.setURI(new URI(
pic2get));
response = client.execute(request);
result = EntityUtils.toString(response.getEntity());
JSONObject json = new JSONObject(result);
Log.e("hey",
json.getJSONObject("data")
.getJSONObject("images")
.getJSONObject(
"standard_resolution")
.getString("url"));
URL url = new URL(json.getJSONObject("data")
.getJSONObject("images")
.getJSONObject("standard_resolution")
.getString("url"));
Bitmap bmp = BitmapFactory.decodeStream(url
.openConnection().getInputStream());
curlikeimage.setImageBitmap(bmp);
curlikeimage.postInvalidate();
} catch (URISyntaxException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
} catch (Exception e) {
}
}
};
thread.start();
}
private OnClickListener buttonClickListener = new OnClickListener() {
@Override
public void onClick(View v) {
getNewPic();
}
};
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.tab1frag, container, false);
Button b = (Button) rootView.findViewById(R.id.button1);
b.setOnClickListener(buttonClickListener);
curlikeimage = (ImageView) rootView.findViewById(R.id.imageView1);
return rootView;
}
}
注意
GetPic方法中的pic2get变量是从服务器返回的JSONObject，它包含实际图像的URL
请注意，获取图像并在imageview中设置它不是（我认为）问题，因为我可以确认它确实设置了它
我过去一天试着寻找很多解决方案，但我找不到另一种适合我的解决方案。