onclick 时将数据从 ListView 传递到活动

Posted 2023-04-19

【中文标题】onclick 时将数据从 ListView 传递到活动

【英文标题】：Passing data from ListView to activity upon onclick

【发布时间】：2019-08-13 17:01:20

【问题描述】：

AuctionList.java

public class AuctionList extends AppCompatActivity 
ListView mListView;
ArrayList<Model> mList;
AuctionListAdapter mAdapter = null;
DatabaseHelperUpload mDBUpload;

TextView txtName,txtDescription,txtDuration,txtPrice;
ImageView imageViewIcon;

@Override
protected void onCreate(Bundle savedInstanceState)
    super.onCreate(savedInstanceState);
    setContentView(R.layout.auction_list);

    mDBUpload = new DatabaseHelperUpload(this);
    mListView = findViewById(R.id.listView);
    mList = new ArrayList<>();
    mAdapter = new AuctionListAdapter(this,R.layout.row,mList);
    mListView.setAdapter(mAdapter);
    txtName = findViewById(R.id.txtName);
    txtDescription = findViewById(R.id.txtDescription);
    txtDuration = findViewById(R.id.txtDescription);
    txtPrice = findViewById(R.id.txtPrice);

mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() 
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) 

            String name = txtName.getText().toString();
            String description = txtDescription.getText().toString();
            String price = txtPrice.getText().toString();
            String duration = txtDuration.getText().toString();
            Intent intent5 = new Intent(AuctionList.this,BuyerHome.class);
            intent5.putExtra("name",name);
            intent5.putExtra("description",description);
            intent5.putExtra("price",price);
            intent5.putExtra("duration",duration);

            startActivity(intent5);
        
    );

Activity.java

Bundle bundle = getIntent().getExtras();

    String duration = bundle.getString("duration");
    String price = bundle.getString("price");

    TextView durationLog = (TextView)findViewById(R.id.text_view_countdown);
    TextView priceLog = (TextView)findViewById(R.id.textPrice);

    durationLog.setText(duration);
    priceLog.setText(price);

模型.java

public class Model 
private int id;
private String name;
private String duration;
private String description;
private String price;
private byte[] image;

public Model(int id, String name,String description,String price,String duration, byte[] image) 
    this.id = id;
    this.name = name;
    this.description = description;
    this.price = price;
    this.duration = duration;
    this.image = image;


public String getDescription() 
    return description;


public void setDescription(String description) 
    this.description = description;


public String getPrice() 
    return price;


public void setPrice(String price) 
    this.price = price;


public int getId() 
    return id;


public void setId(int id) 
    this.id = id;


public String getName() 
    return name;


public void setName(String name) 
    this.name = name;


public String getDuration() 
    return duration;


public void setDuration(String duration) 
    this.duration = duration;



public byte[] getImage() 
    return image;


public void setImage(byte[] image) 
    this.image = image;

activity.java 代码是部分的，因为我仍在尝试。所以我只是想获取两个数据（持续时间和价格）。

但是，我遇到了错误，我的应用程序不断崩溃。请问我的代码有什么问题。我实际上有一个模型代码，如图所示。

错误是：

2019-03-23 00:30:58.046 11048-11048/com.example.jianminmong.aucon E/androidRuntime: FATAL EXCEPTION: main
Process: com.example.jianminmong.aucon, PID: 11048
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.widget.TextView.getText()' on a null object reference
    at com.example.jianminmong.aucon.AuctionList$1.onItemClick(AuctionList.java:63)
    at android.widget.AdapterView.performItemClick(AdapterView.java:318)
    at android.widget.AbsListView.performItemClick(AbsListView.java:1159)
    at android.widget.AbsListView$PerformClick.run(AbsListView.java:3136)
    at android.widget.AbsListView$3.run(AbsListView.java:4052)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6669)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

非常感谢这里的一些帮助，因为这是我最后一年项目的最后一部分。顺便说一句，我是这里的业余爱好者，所以我越需要帮助。

我基本上只是想相应地从列表视图中检索数据并初始化值，&&& 它不应该在我按下它时不断重置数据，因为活动需要它在后台运行（例如计时器)

【参考方案1】：

当您从 Textview 获取文本时，您的 Textview 出现问题，此时任何一个 Textview 都没有与 xml 绑定，这就是您的应用程序崩溃的原因。

   mListView.setOnItemClickListener(new. 
   AdapterView.OnItemClickListener() 
       @Override
         public void onItemClick(AdapterView<?> parent, 
         View view, int position, long id) 

        String name = txtName.getText().toString();
        String description = 
         txtDescription.getText().toString();
        String price = txtPrice.getText().toString();
        String duration = txtDuration.getText().toString();
        Intent intent5 = new Intent(AuctionList.this,BuyerHome.class);
        intent5.putExtra("name",name);
        intent5.putExtra("description",description);
        intent5.putExtra("price",price);
        intent5.putExtra("duration",duration);

        startActivity(intent5);
    
);

【讨论】：

我已经初始化了 alr ，只是我没有在这里展示。还是我误解了你的解释？你能告诉我我应该怎么做吗？我刚刚编辑了显示我的初始化的代码。

我已经知道是什么问题，但我不知道如何解决。我正在从另一个 xml 文件中检索数据。但我无法更改此 java 文件的 xml 文件。有什么办法解决吗？