得意犹堪夸世俗，诏黄新湿字如鸦。这篇文章主要讲述Android - 在寻呼机中获取片段的上下文相关的知识，希望能为你提供帮助。
我有一个使用寻呼机作为导航的android应用程序。对于选项卡，我有3个布局作为内容。其中一个片段是一个画廊，我想添加图像。为此，我必须设置一个ImageAdapter，但我需要知道如何访问片段的上下文。
final LayoutInflater factory = getLayoutInflater();
final View view = factory.inflate(R.layout.pictures, null);
Gallery g = (Gallery) view.findViewById(R.id.gallery1);
g.setAdapter(new ImageAdapter(view.getContext()));
我在onCreate方法中使用上面的代码从不是contentview的布局中获取库。我必须给ImageAdapter一个Context。但是我必须在那里设置什么背景？
编辑：这是我的完整代码：
package com.bw2801.uwelugemediathek;
import java.util.Locale;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Context;
import android.database.DataSetObserver;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.SpinnerAdapter;
import android.widget.Toast;
public class MainActivity extends FragmentActivity implements
ActionBar.TabListener {SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
PicturesSectionFragment ps = new PicturesSectionFragment();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0;
i <
mSectionsPagerAdapter.getCount();
i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}final LayoutInflater factory = getLayoutInflater();
final View view = factory.inflate(R.layout.pictures, null);
Gallery g = (Gallery) view.findViewById(R.id.gallery1);
g.setAdapter(new ImageAdapter(ps.getActivity()));
}public class ImageAdapter extends BaseAdapter {
private Context mContext;
private Integer[] mImageIds = {
R.drawable.image01,
R.drawable.image02,
R.drawable.image03,
R.drawable.image04,
R.drawable.image05,
R.drawable.image06,
R.drawable.image07,
R.drawable.image08,
};
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);
i.setImageResource(mImageIds[position]);
i.setLayoutParams(new Gallery.LayoutParams(150, 100));
i.setScaleType(ImageView.ScaleType.FIT_XY);
return i;
}
}@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 onTabSelected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}@Override
public Fragment getItem(int position) {
switch(position) {
case 0:
return new DummySectionFragment();
case 1:
return new SoundSectionFragment();
case 2:
return ps;
}
return new DummySectionFragment();
}@Override
public int getCount() {
return 3;
}@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Informationen";
case 1:
return "Soundboard";
case 2:
return "Galerie";
}
return null;
}
}public static class DummySectionFragment extends Fragment {public DummySectionFragment() {
}@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.info, container, false);
}
}public static class PicturesSectionFragment extends Fragment {public PicturesSectionFragment() {
}@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.pictures, container, false);
}
}public static class SoundSectionFragment extends Fragment {public SoundSectionFragment() {
}@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.sounds, container, false);
}
}
}
答案片段没有自己的Context，它们使用父Activity。
- 要获取父活动上下文，请使用
getActivity() - 要使用应用程序上下文，请使用
getActivity().getApplicationContext()
更新：
当且仅当所述片段当前附加到活动时，片段的
getActivity()返回一个Activity实例。所以，
Fragment f = new MyFragment();
创建一个片段，但它尚未附加到一个活动。因此
f.getActivity()返回null。添加到活动后：
getFragmentManager().beginTransaction().add(f,"fragment").commit();
现在，
getActivity()将返回一个Activity实例。再次，如果我们从Activity中分离片段：
getFragmentManager().beginTransaction().detach(f).commit()
getActivity()将再次返回null值。因此，我们不应该在
getActivity()类之外使用Fragment，因为我们无法确定附加状态。因此，我建议你在其方法中使用getActivity()片段自己的类：onAttach()，onCreate()或onActivityCreated()。另一答案你可以这样使用
g.setAdapter(new ImageAdapter(getActivity()));
另一答案获取我发现的片段上下文的最简单，最精确的方法是在调用onCreateView方法时直接从ViewGroup获取它，至少在这里你肯定不会为getActivity（）获取null
public class Animal extends Fragment {Context thiscontext;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {thiscontext = container.getContext();
另一答案
write under code in Your CoreApplication.javastep1)
public class CoreApplication extends Application {private static CoreApplication instance;
}step2) onCreate(){instance = this;
}step3 )
add under method()
【Android - 在寻呼机中获取片段的上下文】public static CoreApplication getGlobalApplicationContext（）{
if (instance == null) {
throw new IllegalStateException("this application does not
inherit GlobalApplication");
" +
"}return instance;
}Step4)
g.setAdapter(new ImageAdapter(getGlobalApplicationContext()));
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