这是我的代码：
PostTweetDialog.java
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import com.codepath.apps.mysimpletweet.models.Tweet;
import com.loopj.android.http.AsyncHttpResponseHandler;
import com.loopj.android.http.JsonHttpResponseHandler;
import org.apache.http.Header;
import org.json.JSONObject;
import java.util.ArrayList;
/**
* Created by AlecksJohanssen on 4/1/2016.
*/
public class PostTweetDialog extends DialogFragment {
private RestClient client;
private PostTweetInterface dialogFragment;
ArrayList<Tweet> tweets;
TweetArrayAdapter adapter;
public Dialog onCreateDialog(Bundle savedInstanceState) {
LayoutInflater inflater = getActivity().getLayoutInflater();
View dialogView = inflater.inflate(R.layout.post_tweet, null);
EditText etComposeTweet = (EditText) dialogView.findViewById(R.id.posttxt);
final String body = String.valueOf(etComposeTweet.getText());
tweets = new ArrayList<>();
adapter = new TweetArrayAdapter(tweets);
AlertDialog.Builder TweetDialog = new AlertDialog.Builder(getActivity());
TweetDialog.setTitle("Post Tweet");
TweetDialog.setView(dialogView)
.setPositiveButton("Continue", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
client.postTweet(body, new JsonHttpResponseHandler() {
@Override
public void onSuccess(int statusCode, Header[] headers, JSONObject json) {
Tweet myNewTweet = Tweet.fromJSON(json);
Log.d("DEBUG",String.valueOf(json.toString()));
tweets.add(myNewTweet);
adapter.notifyDataSetChanged();
}
@Override
public void onFailure(int statusCode, Header[] headers, Throwable throwable, JSONObject errorResponse) {
Log.d("Error", errorResponse.toString());
}
});
}
}).setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
dialogFragment.onDialogNegativeClick(PostTweetDialog.this);
}
});
return TweetDialog.create();
}
这是我的PostTweet方法：
public void postTweet(String body, AsyncHttpResponseHandler handler) {
String apiUrl = getApiUrl("statuses/update.json");
RequestParams params = new RequestParams();
params.put("status", body);
getClient().post(apiUrl, params, handler);
}
post_tweet.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<EditText
android:id="@+id/posttxt"
android:inputType="text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:layout_marginLeft="4dp"
android:layout_marginRight="4dp"
android:layout_marginBottom="4dp"
android:hint="Input your Tweet here" />
</LinearLayout>
TimelineActivity.java
public class TimelineActivity extends AppCompatActivity {
private PostTweetDialog PostDialog = new PostTweetDialog();
private RestClient client;
private ArrayList<Tweet> Tweet;
private TweetArrayAdapter taAdapter;
private RecyclerView rvItems;
private TabLayout tabLayout;
private ViewPager viewPager;
private int[] tabIcons = {
R.drawable.ic_tab_favourite,
R.drawable.ic_tab_call,
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_timeline);
rvItems = (RecyclerView) findViewById(R.id.rvItems);
Tweet = new ArrayList<>();
taAdapter = new TweetArrayAdapter(Tweet);
rvItems.setAdapter(taAdapter);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
setupTabIcons();
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
rvItems.setLayoutManager(new LinearLayoutManager(this));
client = RestApplication.getRestClient();
populateTimeline(1);
rvItems.addOnScrollListener(new EndlessRecyclerViewScrollListener(linearLayoutManager) {
@Override
public void onLoadMore(int page, int totalItemsCount) {
populateTimeline(page);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
public void doThis(MenuItem item)
{
PostDialog.show(getFragmentManager(), "fragment_dialog");
}
private void populateTimeline(int page) {
client.getHomeTimeline(new JsonHttpResponseHandler() {
@Override
public void onSuccess(int statusCode, Header[] headers, JSONArray response) {
Tweet.addAll(com.codepath.apps.mysimpletweet.models.Tweet.fromJSONArray(response));
int curSize = taAdapter.getItemCount();
taAdapter.notifyItemRangeInserted(curSize, Tweet.size() - 1);
}
@Override
public void onFailure(int statusCode, Header[] headers, Throwable throwable, JSONArray errorResponse) {
}
}, page);
}
private void setupTabIcons() {
tabLayout.getTabAt(0).setIcon(tabIcons[0]);
tabLayout.getTabAt(1).setIcon(tabIcons[1]);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new OneFragment(), "ONE");
adapter.addFrag(new TwoFragment(), "TWO");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFrag(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
}
} 我不知道为什么我不能使用我的postTweet方法，它总是返回null值。 这是错误NullValue
的gif提前致谢：D。
P / S：它在此行client.postTweet(body, new JsonHttpResponseHandler() {
答案 0 :(得分：0)
如评论中所述，您没有在对话框类中初始化客户端。您可以更改活动代码以将客户端作为参数传递：
public class TimelineActivity extends AppCompatActivity {
private PostTweetDialog PostDialog;
private RestClient client;
private ArrayList<Tweet> Tweet;
private TweetArrayAdapter taAdapter;
private RecyclerView rvItems;
private TabLayout tabLayout;
private ViewPager viewPager;
private int[] tabIcons = {
R.drawable.ic_tab_favourite,
R.drawable.ic_tab_call,
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_timeline);
rvItems = (RecyclerView) findViewById(R.id.rvItems);
Tweet = new ArrayList<>();
taAdapter = new TweetArrayAdapter(Tweet);
rvItems.setAdapter(taAdapter);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
setupTabIcons();
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
rvItems.setLayoutManager(new LinearLayoutManager(this));
client = RestApplication.getRestClient();
PostDialog = new PostTweetDialog(client);
...
}
...
}
并在对话框类中添加一个相应的构造函数：
public class PostTweetDialog extends DialogFragment {
private RestClient client;
private PostTweetInterface dialogFragment;
ArrayList<Tweet> tweets;
TweetArrayAdapter adapter;
public PostTweetDialog(RestClient client) {
this.client = client;
}
...
}
<强>更新
为了解答您的问题，为什么client为null：
让我们看一下PostTweetDialog的代码......
在该类的第一行中，您声明私有变量client：
private RestClient client;
然后在onCreate中设置使用onClick的{{1}}回调。
client但是，在课程 TweetDialog.setView(dialogView)
.setPositiveButton("Continue", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
client.postTweet(body, new JsonHttpResponseHandler() { ... });
中没有任何地方可以找到该可变的作业。因此，PostTweetDialog PostTweetDialog内的client始终未定义。
由于您可能希望使用活动使用的相同null，因此您有多种选择。
RestClient引用传递给对话框类。client，并在已有OnClickListener的活动中实施onClick。但是，您需要将活动的引用传递给对话框类。