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我试图在这个网站的许多其他问题，但今天他们都不是有帮助的，我似乎有其他人的作品，但每一次我打一次发送（当我想相同的语法我的文本字段更新）我的应用程序崩溃，只是，我已经尝试了很多不同的语法为setText（）方法，但没有奏效。.setText（）崩溃我的Android应用
感谢所有帮助提前
这是我的主类
package com.example.myapp;
import android.app.Activity;
import java.io.IOException;
import java.util.ArrayList;
import android.app.Activity;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.*;
import org.apache.http.client.methods.*;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
public class TestprojectsActivity extends Activity {
private int index;
private int QsClicked = 0;
private ArrayList<String> categories = new ArrayList<String>();
private ArrayList<Button> buttons = new ArrayList<Button>();
Button b1;
Button b2;
Button b3;
Button b4;
Button changer;
private int Qselected;
TextView txt;
EditText edit;
private ArrayList<String> questions = new ArrayList<String>();
private int qnum = 0;
// updates all the buttons so we can see more categories
public void updateButtons(View v){
for(int i = 0; i < 4; i++){
if(index >= categories.size()){
index = 0;
}
buttons.get(i).setText(categories.get(index));
index++;
}
}
public void Q1(View v){
setContentView(R.layout.sub);
Qselected = index;
//send(null);
}
public void Q2(View v){
setContentView(R.layout.sub);
Qselected = (index+1);
//send(null);
}
public void Q3(View v){
setContentView(R.layout.sub);
Qselected = (index+2);
//send(null);
}
public void Q4(View v){
setContentView(R.layout.sub);
Qselected = (index+3);
//send(null);
}
public void send(View v){
edit.setText("WHY ISNT THIS WORKING?");
if(qnum < questions.size()){
txt.setText("i work!");
qnum++;
}
else{
qnum = 0;
System.exit(0);
}
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
index = 0;
b1 = (Button) findViewById(R.id.B1);
buttons.add(b1);
b2 = (Button) findViewById(R.id.B2);
buttons.add(b2);
b3 = (Button) findViewById(R.id.B3);
buttons.add(b3);
b4 = (Button) findViewById(R.id.B4);
buttons.add(b4);
txt = (TextView) findViewById(R.id.textView1);
edit = (EditText) findViewById(R.id.editText2);
categories.add("dumb questions");
categories.add("smart questions");
questions.add("hi there, what is your name?");
questions.add("what did you have for breakfast today?");
questions.add("how old are you?");
questions.add("what color is your hair?");
updateButtons(null);
}
}
这是我的主XML
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/layoutrowtop"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<Button
android:id="@+id/B4"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="B4"
android:onClick="Q4" />
<Button
android:id="@+id/B3"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="B3"
android:onClick="Q3" />
<Button
android:id="@+id/B2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="B2"
android:onClick="Q2" />
<Button
android:id="@+id/B1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="B1"
android:onClick="Q1" />
<Button
android:id="@+id/Button05"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="More Categories"
android:onClick="updateButtons" />
</LinearLayout>
这是我的子XML（我用它，所以我可以有另一种布局）
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/textView1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0.22"
android:text="Question"
/>
<EditText
android:id="@+id/editText2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0.51"
android:ems="10"
android:inputType="text" />
<Button
android:id="@+id/send"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0.08"
android:text="Send"
android:onClick="send" />
</LinearLayout>
线
您可以发布您的logcat异常堆栈 – Tarun
[为什么空指针异常？]（http://samir-mangroliya.blogspot.in/p/why-nullpointerexception-occures- in.html） –