动态更改片断内部的ImageView-还是动态生成片断？

Question

我是android编程的新手。虽然我在Access上搜索了这个问题，但没有找到任何令人满意的解决方案：

问题是：我想动态地将一个图像设置为imageview--它位于一个片段中。

我想使用图像的文件名来完成这个操作。

但我得到了NullPointerException：

java.lang.NullPointerException：尝试对空对象引用调用虚拟方法“void android.widget.imageView.SetImageResource(int)”

下面是我的代码。如果有人回应我会很高兴。

activity班：

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);
            }
        });
    }
}

片段类：

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 14:11:18.822 121 01-12101/com.codeforlite.virdlerim E/AndroidRuntime：致命异常：主
进程：com.codeforlite.virdlerim,PID:12101

java.lang.NullPointerException：尝试对空对象引用调用虚拟方法“void android.widget.imageView.SetImageResource(int)”

在com.codeforlite.virdlerim.fragment_arabic_image.onCreateView(Fragment_arabic_image.:46)
在AndroidX.fragment.app.fragment.performCreateView(Fragment.Java:2600)
在AndroidX.fragment.app.fragmentManagerimpl.moveToState（FragmentManagerimpl.Java:881)
在AndroidX.fragment.app.fragmentManagerimpl.moveToExpectedState（spatchStateChange（FragmentManagerImpl.java:2663)
在AndroidX.Fragment.app.FragmentManagerImpl.java:2613)
在AndroidX.Fragment.app.FragmentController.DispatchActivityCreated（FragmentController.DispatchActivityCreated（FragmentController.java:246)
在AndroidX.Fragment.app.FragmentActivity.OnStart（FragmentActivity.java:542)
在ransactionexecutor.execute（Transactionexecutor.java:97)
在android.app.activitythread$H.HandleMessage（activitythread.java:2220)
在android.os.handler.dispatchmessage（handler.java:107)
在android.os.looper.loop（looper.java:237)
在android.app.activitythread.main（activitythread.java:8016)
在

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“img_arabic_text”的id属性

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