所以我正在开发一款需要SeekBar的应用。此SeekBar位于片段内，并在用户单击下拉按钮时显示。 SeekBar出现并且工作正常。但是，一旦我尝试使用此搜索栏，我就会崩溃。我想要什么来获得条形图的进度，并根据所述条形图的进度显示文本。但是我在发布时遇到了这个崩溃
07-14 10:18:47.650: D/AndroidRuntime(924): Shutting down VM
07-14 10:18:47.650: W/dalvikvm(924): threadid=1: thread exiting with uncaught exception (group=0xb3a47b90)
07-14 10:18:47.670: E/AndroidRuntime(924): FATAL EXCEPTION: main
07-14 10:18:47.670: E/AndroidRuntime(924): Process: com.example.tipquiz, PID: 924
07-14 10:18:47.670: E/AndroidRuntime(924): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tipquiz/com.example.tipquiz.MainActivity}: java.lang.NullPointerException
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.ActivityThread.access$700(ActivityThread.java:135)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.os.Handler.dispatchMessage(Handler.java:102)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.os.Looper.loop(Looper.java:137)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.ActivityThread.main(ActivityThread.java:4998)
07-14 10:18:47.670: E/AndroidRuntime(924): at java.lang.reflect.Method.invokeNative(Native Method)
07-14 10:18:47.670: E/AndroidRuntime(924): at java.lang.reflect.Method.invoke(Method.java:515)
07-14 10:18:47.670: E/AndroidRuntime(924): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
07-14 10:18:47.670: E/AndroidRuntime(924): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
07-14 10:18:47.670: E/AndroidRuntime(924): at dalvik.system.NativeStart.main(Native Method)
07-14 10:18:47.670: E/AndroidRuntime(924): Caused by: java.lang.NullPointerException
07-14 10:18:47.670: E/AndroidRuntime(924): at com.example.tipquiz.MainActivity.onCreate(MainActivity.java:36)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.Activity.performCreate(Activity.java:5243)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
07-14 10:18:47.670: E/AndroidRuntime(924): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
07-14 10:18:47.670: E/AndroidRuntime(924): ... 11 more
现在我怀疑它崩溃的原因是因为我在我的主类中运行所有这些代码，而不是片段类，但当我尝试将代码移到片段类时，我遇到了错误findViewById行。
这是我的代码：
我的主要课程
package com.example.tipquiz;
import android.app.Activity;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.ImageView;
import android.widget.RatingBar;
import android.widget.RatingBar.OnRatingBarChangeListener;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
public class MainActivity extends Activity implements OnRatingBarChangeListener, OnSeekBarChangeListener {
// Testing Stuff to show the rating value, will need to use later for maths
RatingBar rb;
TextView tv;
SeekBar fqBar;
TextView fqTV;
// The Image used as the DropDown button, Rotate code below
ImageView dropDownButton;
Boolean hasRotated = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dropDownButton = (ImageView) findViewById(R.id.dropDownButton);
fqBar = (SeekBar)findViewById(R.id.seekBarFQ);
fqBar.setOnSeekBarChangeListener(this);
fqTV = (TextView)findViewById(R.id.textViewFQ2);
}
@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;
}
FragmentManager fm = getFragmentManager();
QuizFragment qf = new QuizFragment();
public void dropDown(View view){
if(hasRotated == false){
FragmentTransaction ft = fm.beginTransaction();
ft.setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out);
dropDownButton.setRotation(90);
ft.add(R.id.quizFragment, qf);
ft.show(qf);
ft.commit();
hasRotated = true;
}else if(hasRotated == true){
FragmentTransaction ft = fm.beginTransaction();
ft.setCustomAnimations(android.R.animator.fade_out, android.R.animator.fade_out);
dropDownButton.setRotation(0);
hasRotated = false;
ft.remove(qf);
ft.commit();
}
}
@Override
public void onRatingChanged(RatingBar ratingBar, float rating,
boolean fromTouch) {
// final int numStars = ratingBar.getNumStars();
tv.setText(rating + "/5.0");
}
// http://www.compiletimeerror.com/2013/08/android-rating-bar-example.html#.U7SZ5fldXm4
// http://custom-android-dn.blogspot.ca/2013/01/how-to-use-and-custom-ratingbar-in.html
@Override
public void onProgressChanged(SeekBar arg0, int progress, boolean fromUser) {
if(progress > 70 && progress < 90){
fqTV.setText("Above Average");
}else if(progress > 40 && progress <= 70){
fqTV.setText("Average");
}else if(progress <= 40){
fqTV.setText("Awful");
}
}
@Override
public void onStartTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
@Override
public void onStopTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
}
主要XML文件：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#bbcde3"
android:orientation="vertical" >
<GridLayout
android:id="@+id/gridLayout1"
android:layout_width="fill_parent"
android:layout_height="35dip"
android:background="#e3e3e3"
android:columnCount="2"
android:gravity="right"
android:orientation="horizontal" >
<Button
android:id="@+id/button1"
android:layout_width="108dp"
android:layout_height="match_parent"
android:layout_column="1"
android:layout_gravity="right|top"
android:layout_row="0"
android:background="#3fa9f5"
android:fontFamily="helvetica"
android:text="@string/settings_button"
android:textColor="#ffffff"
android:textSize="14sp"
android:textStyle="bold" />
</GridLayout>
<Space
android:layout_width="match_parent"
android:layout_height="12sp" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView2"
android:layout_below="@+id/gridLayout1"
android:layout_marginTop="24dp"
android:text="@string/rys"
android:textColor="#888888"
android:textSize="19sp" />
<RatingBar
android:id="@+id/ratingBar1"
style="@style/circleRatingBar"
android:layout_width="wrap_content"
android:layout_height="47dp"
android:layout_alignLeft="@+id/textView1"
android:layout_below="@+id/textView1"
android:numStars="5"
android:rating="3.0"
android:stepSize="1.0" />
<ImageView
android:id="@+id/dropDownButton"
android:layout_width="48dip"
android:layout_height="48dip"
android:layout_alignBottom="@+id/ratingBar1"
android:layout_toRightOf="@+id/ratingBar1"
android:onClick="dropDown"
android:src="@drawable/ddb" />
<RelativeLayout
android:id="@+id/dropDownLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignTop="@+id/textView2"
android:visibility="gone" >
<TextView
android:id="@+id/testTV"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Testing dropdown" />
</RelativeLayout>
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/ratingBar1"
android:layout_marginLeft="14dp"
android:layout_marginTop="16dp"
android:text="@string/tipTitle"
android:textColor="#888888"
android:textSize="19sp" />
<FrameLayout
android:id="@+id/quizFragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/dropDownButton" />
</RelativeLayout>
片段类和XML
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/textViewFQ"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="24dp"
android:layout_marginLeft="12dp"
android:text="@string/food_quality"
android:textColor="#888888"
android:textSize="19sp" />
<TextView
android:id="@+id/textViewFQ2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textViewFQ"
android:layout_marginTop="24dp"
android:layout_marginLeft="5dp"
android:textColor="#888888"
android:textSize="19sp" />
<SeekBar
android:id="@+id/seekBarFQ"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/textViewFQ"
android:layout_marginLeft="12sp"
android:layout_marginRight="12sp"
android:layout_marginTop="24dp"
android:background="#f0f0f0"
android:progressDrawable="@xml/progress_drawable"
android:thumb="@xml/thumb_drawable"
android:max="100"
android:progress="15" />
</RelativeLayout>
package com.example.tipquiz;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
public class QuizFragment extends Fragment{
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.quiz_fragment_layout, container, false);
}
}
任何帮助将不胜感激！
答案 0 :(得分：1)
你没有获得搜索栏，因为它是片段xml。
您需要在onCreateView中找到它：
View view = inflater.inflate(R.layout.quiz_fragment_layout, container, false);
fqBar = (SeekBar) view.findViewById(R.id.seekBarFQ);
希望它有所帮助。
答案 1 :(得分：-1)
问题在于这行代码
tv.setText（评级+“/ 5.0”）;
在onRatingChanged方法中，你刚刚声明了TextView tv但从未初始化它。