gson.fromJson(getIntent().getStringExtra() 返回 null

Question

我正在将对象从SurfaceInspectionListActivity 发送到AddSurfaceInspectionActivity

在 putExtra 上我可以在调试模式下看到数据，但是在检索数据时我得到 NULL

我尝试将其作为字符串获取，以进行也导致 NULL 的测试

surfaceObjString = getIntent().getStringExtra("myjsonSurfaceObject2");

这是SurfaceInspectionListActivity Intent 代码

public void addSurfaceInspection(View view) {

        Intent intent = new Intent(SurfaceInspectionListActivity.this, AddSurfaceInspectionActivity.class);
        intent.putExtra("myjsonSurfaceObject2", surfaceObject);
        startActivity(intent);
        finish();
    }

这是AddSurfaceInspectionActivity上的检索码

 Gson gson = new Gson();
        surfaceObj = gson.fromJson(getIntent().getStringExtra("myjsonSurfaceObject2"), Surfaces.class);

Answer 1

试试看：

public void addSurfaceInspection(View view) {

    Intent intent = new Intent(SurfaceInspectionListActivity.this, AddSurfaceInspectionActivity.class);
     Gson gson = new Gson();
   String sruface = gson.toJson(surfaceObject, Surfaces.class);
    intent.putExtra("myjsonSurfaceObject2", sruface );
    startActivity(intent);
    finish();
}

Answer 2

首先通过实现Serializable接口使SurfacesSerializable。然后改SurfaceInspectionListActivity：

public void addSurfaceInspection(View view) {

    Intent intent = new Intent(SurfaceInspectionListActivity.this, AddSurfaceInspectionActivity.class);

    Bundle bundle = new Bundle();
    bundle.putSerializable("myjsonSurfaceObject2", surfaceObject);

    intent.putExtras(bundle);

    startActivity(intent);
    finish();
}

为了Surface对象在AddSurfaceInspectionActivity：

Surface surface = getIntent().getSerializableExtra("myjsonSurfaceObject2");

Answer 3

试试这个：

1. 使用 Gson 将您的对象转换为 JSON
2. 将其传递给活动

3. 在 SurfaceInspectionListActivity 中，使用 Gson 将其转换回对象

   public void addSurfaceInspection(View view) {
   
   Intent intent = new Intent(SurfaceInspectionListActivity.this, AddSurfaceInspectionActivity.class);
   //Convert to string
   Gson gson = new Gson();
   String json = gson.toJson(surfaceObject);
   intent.putStringExtra("myjsonSurfaceObject2", json);
   startActivity(intent);
   finish();
   }
   

在AddSurfaceInspectionActivity:

 Gson gson = new Gson();
 surfaceObj = gson.fromJson(getIntent().getStringExtra("myjsonSurfaceObject2"), Surfaces.class);

Answer 4

如果您已经在使用实现了Serializable 的对象，则不再需要使用 Gson。只需使用putExtra() 和getExtra()。像这样的：

// there is nothing need to be changed here.
public void addSurfaceInspection(View view) {
    Intent intent = new Intent(SurfaceInspectionListActivity.this, AddSurfaceInspectionActivity.class);
    intent.putExtra("myjsonSurfaceObject2", surfaceObject);
    startActivity(intent);
    finish();
}

然后获取对象：

Bundle bundle = intent.getExtra();
surfaceObj = (Surfaces) bundle.getSerializable("myjsonSurfaceObject2");

---

如果 Gson 是您的先决条件，那么您可以使用以下内容：

 // get the String of object
public static String convertToGsonString(Surface surfaceObject) {
  Gson gson = new Gson();
  return gson.toJson(surfaceObject);
}

// convert to object from String
public static Surface convertToObjectFromString(String objString) {
  Type type = new TypeToken<Surface>() {}.getType();

  Gson gson = new Gson();
  return gson.fromJson(objString, type);
}

那么就可以使用上面的方法发送intent了：

public void addSurfaceInspection(View view) {
    Intent intent = new Intent(SurfaceInspectionListActivity.this, AddSurfaceInspectionActivity.class);
    intent.putExtra("myjsonSurfaceObject2", convertToGsonString(surfaceObject));
    startActivity(intent);
    finish();
}

然后接收它：

 Bundle extra = getIntent().getExtra();
 String objString = extra.getString("myjsonSurfaceObject2");

 surfaceObj = convertToObjectFromString(objString);

请注意，使用 Gson 时不需要使用 Serializable。