动态更改片段内部的ImageView，还是动态生成片段

Question

我是android编程的新手。尽管我在实现上搜索了这个问题，但我找不到任何令人满意的解决方案：

问题是：我想动态地将图像设置为imageview，它位于片段中。

我想使用图像的文件名来完成这项工作。

但我得到了NullPointerException：

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法"void android.widget.ImageView.setImageResource(int(">

下面显示了我的代码。如果有人回应，我会很高兴。

活动类别：

public class Oku extends AppCompatActivity {
private int hedefSayi;
private int actualNumber;
private FragmentManager fragmentManager;
private Fragment tempFragment;
private BottomNavigationView bottomNavigationView;
private FrameLayout fragmentContainer;
private ProgressBar progressBar;
private Button btn_tıkla;
private Vird comingVird;
private Fragment arabicImageFragment;
private Fragment turkishTextFragment;
private Fragment anlamFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_oku);
comingVird= (Vird) getIntent().getSerializableExtra("Vird.class");
hedefSayi=200;
actualNumber=hedefSayi;
fragmentContainer=findViewById(R.id.fragment_container);
bottomNavigationView=findViewById(R.id.bottom_navi);
arabicImageFragment=new Fragment_Arabic_Image(comingVird.getImageName());

//put the arabic image fragment on the container first
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container,arabicImageFragment).commit();

//on navigation item selected:
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {

//get the selected items id number
int itemID=item.getItemId();
//if id number is related to the arabic image fragment, set the temp fragment as arabic image fragment
if(itemID==R.id.action_oku_arapca){
tempFragment=new Fragment_Arabic_Image(comingVird.getImageName());
}
//if id number is related to turkish text fragment, set the related fragment
else if(itemID==R.id.action_oku_turkce) { tempFragment=new Fragment_Turkce_Okunus();}
//if id number is related to the meaning set related fragment..
else if(itemID==R.id.action_oku_anlamı){ tempFragment=new Fragment_Anlam();}
//replace the fragment on the container with the temp fragment
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,tempFragment).commit();
return true;
}
});
//initiate progress bar with full progress
progressBar=findViewById(R.id.progressBar);
progressBar.setProgress(100);
btn_tıkla=findViewById(R.id.button_tıkla);
btn_tıkla.setText(""+actualNumber);
//on button click
btn_tıkla.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
progressBar.setProgress(100*actualNumber/hedefSayi);
//decrease the number and set on the text of the button
actualNumber--;
btn_tıkla.setText(""+actualNumber);
//her button tıklamada kısa titreşim ver
Vibrator vb = (Vibrator)   getSystemService(Context.VIBRATOR_SERVICE);
vb.vibrate(100);
}
});
}
}

碎片类别：

public class Fragment_Arabic_Image extends Fragment {
private String imageName;
private ImageView arabicText_Image;
private int imageid;

public Fragment_Arabic_Image(String imageName) {
this.imageName = imageName;
}
@SuppressLint("ResourceType")
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment_arabic_image,container,false);
imageid=getActivity().getResources().getIdentifier(imageName,"drawable",getActivity().getPackageName());
arabicText_Image=view.findViewById(R.id.img_arabic_text);
arabicText_Image.setImageResource(this.imageid);//this line causes error
return view;
}
}

错误消息：

2020-08-04 14:11:18.822 12101-12101/com.codeforlite.virdlerim E/AndroidRuntime：致命异常：main
进程：com.codeforlite.virdlerin，PID:12101

java.lang.NullPointerException：尝试在null对象引用上调用虚拟方法"void android.widget.ImageView.setImageResource(int(">

在androidx.Fragment.app.Fragment.performCreateView(Fragment.java:2600(
androidx.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:881(
androidx.fragment.app.FragmentManagerImpl.moveToStateandroidx.fragment.app.FragmentManagerImpl.removeRundantOperationsAndExecute(FragmentManagerImpl.java:1824(FragmentManagerImpl.java:2613(
androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentControlr.java:246(
androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:542(
1androidx.appcompat.app.AppCompatActivity.onStartandroid.app.Activity.performStart(Activity.java:7980android.app.servertransaction.TransactionExecutor.executeLifecycleStateandroid.app.ActivityThread.main(ActivityThreads.java:8016(
在java.lang.reflect.Method.ioke(Native Method(
com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run

Answer 1

ImageViewarabicText_Image似乎没有正确初始化。检查fragment_arabic_image.xml。确保ImageView具有值为"的id属性；img_阿拉伯语文本">

<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/img_arabic_text" />