OnClick（）不适用于货币转换器。
我想在我的应用的侧边菜单中添加货币转换器。但是我在点击（）之后无法获得转换。 点击＆＃34;计算＆＃34;我没有得到转换。 请参阅代码为什么我无法点击。我用过雅虎api。
CurrencyConverter.java
import android.app.Fragment;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import info.androidhive.customlistviewvolley.R;
public class CurrencyConverter extends Fragment {
public CurrencyConverter() {
}
TextView t;
public int to;
public int from;
public String[] val;
public String s;
public Handler handler;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.currency_converter, container, false);
t= (TextView) rootView.findViewById(R.id.textView4);
Spinner s1 = (Spinner) rootView.findViewById(R.id.spinner1);
Spinner s2 = (Spinner) rootView.findViewById(R.id.spinner2);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this.getActivity(), R.array.name, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.select_dialog_singlechoice);
val = getResources().getStringArray(R.array.value);
s1.setAdapter(adapter);
s2.setAdapter(adapter);
s1.setOnItemSelectedListener(new spinOne(1));
s2.setOnItemSelectedListener(new spinOne(2));
Button b = (Button) rootView.findViewById(R.id.button1);
b.setOnClickListener(new View.OnClickListener() {
public void onClick(View rootView) {
//t.setText(exResult);
if (from == to) {
Toast.makeText(getActivity().getApplicationContext(), "Invalid", 4000).show();
} else {
try {
// s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject jObj;
jObj = new JSONObject(s);
String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
t.setText(exResult);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
return rootView;
}
public class calculate extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(String... args) {
try {
s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject jObj;
jObj = new JSONObject(s);
String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
// t.setText(exResult);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return s;
}
@Override
protected void onPostExecute(String exResult) {
// t = (TextView) rootView.findViewById(R.id.textView4);
// t.setText(exResult);
}
}
public String getJson(String url)throws ClientProtocolException, IOException {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return build.toString();
}
public class spinOne implements AdapterView.OnItemSelectedListener
{
int ide;
spinOne(int i)
{
ide =i;
}
public void onItemSelected(AdapterView<?> parent, View view,
int index, long id) {
if(ide == 1)
from = index;
else if(ide == 2)
to = index;
}
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
}
CurrencyConverter.xml
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#FFFFFF"
>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:background="#FFFFFF">
<TextView
android:id="@+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/one"
android:textAppearance="?android:attr/textAppearanceLarge" />
<Spinner
android:id="@+id/spinner1"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/in"
android:textAppearance="?android:attr/textAppearanceLarge" />
<Spinner
android:id="@+id/spinner2"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/equal"
android:textAppearance="?android:attr/textAppearanceLarge" />
<RelativeLayout
android:id="@+id/relativeLayout1"
android:layout_width="match_parent"
android:layout_height="122dp"
android:gravity="center"
android:background="#ffffff">
<RelativeLayout
android:id="@+id/relativeLayout2"
android:layout_width="match_parent"
android:layout_height="120dp"
android:gravity="center"
android:background="#ffffff">
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="@string/result"
android:textSize="35dp"
/>
</RelativeLayout>
</RelativeLayout>
<Button
android:id="@+id/button1"
android:layout_marginTop="10dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/calculate" />
</LinearLayout>
</ScrollView>
错误：
05-09 17:33:30.425 2238-2238/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: info.androidhive.customlistviewvolley, PID: 2238
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
at org.json.JSONTokener.nextValue(JSONTokener.java:94)
at org.json.JSONObject.<init>(JSONObject.java:156)
at org.json.JSONObject.<init>(JSONObject.java:173)
at info.androidhive.customlistviewvolley.model.CurrencyConverter$1.onClick(CurrencyConverter.java:74)
at android.view.View.performClick(View.java:4756)
at android.view.View$PerformClick.run(View.java:19749)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-09 17:33:30.430 1233-1513/? W/ActivityManager: Force finishing activity info.androidhive.customlistviewvolley/.MainActivity
2 个答案:
答案 0 :(得分：1)
您正尝试从没有连接的UI线程调用String。作为可能的解决方法之一，您可以创建全局变量并在
分配给它 @Override
protected void onPostExecute(String exResult) {
// t = (TextView) rootView.findViewById(R.id.textView4);
// t.setText(exResult);
globalString = exResult;
}
之后您可以使用它代码。请阅读AsyncTask生命周期和Android Threads。
答案 1 :(得分：0)
更新答案：
CurreencyConverter.java
import android.app.Fragment;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import info.androidhive.customlistviewvolley.R;
public class CurrencyConverter extends Fragment {
public CurrencyConverter() {
}
TextView t;
public int to;
public int from;
public String[] val;
public String s;
String exResult;
public Handler handler;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.currency_converter, container, false);
t= (TextView) rootView.findViewById(R.id.textView4);
Spinner s1 = (Spinner) rootView.findViewById(R.id.spinner1);
Spinner s2 = (Spinner) rootView.findViewById(R.id.spinner2);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this.getActivity(), R.array.name, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.select_dialog_singlechoice);
val = getResources().getStringArray(R.array.value);
s1.setAdapter(adapter);
s2.setAdapter(adapter);
s1.setOnItemSelectedListener(new spinOne(1));
s2.setOnItemSelectedListener(new spinOne(2));
Button b = (Button) rootView.findViewById(R.id.button1);
b.setOnClickListener(new View.OnClickListener() {
public void onClick(View View) {
if (from == to) {
Toast.makeText(getActivity().getApplicationContext(), "Invalid", 4000).show();
} else {
new calculate().execute();
}
}
});
return rootView;
}
public class calculate extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(String... args) {
try {
s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject jObj;
jObj = new JSONObject(s);
exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return exResult;
}
@Override
protected void onPostExecute(String exResult) {
t.setText(exResult);
}
}
public String getJson(String url)throws IOException {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return build.toString();
}
public class spinOne implements AdapterView.OnItemSelectedListener
{
int ide;
spinOne(int i)
{
ide =i;
}
public void onItemSelected(AdapterView<?> parent, View view,
int index, long id) {
if(ide == 1)
from = index;
else if(ide == 2)
to = index;
}
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
}
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