Question

我遇到变量问题：URL_STRING。我似乎无法将另一个变量的值添加到URL_String。由于某种原因它只是空的。非常感谢您的协助。

public class HomeScreen extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
ListView listView;
Spinner spinner;
EditText search;
Button bt;

String URL_STRING;
String entity;
String term;


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

    listView = (ListView) findViewById(R.id.listView);
    spinner = (Spinner) findViewById(R.id.spinner);
    search = (EditText) findViewById(R.id.search);
    term = search.getText().toString();
    bt = (Button) findViewById(R.id.searchBtn);


    ArrayAdapter<CharSequence> entityAdapter = ArrayAdapter
            .createFromResource(this, R.array.Entities,
                    android.R.layout.simple_spinner_item);
    spinner.setAdapter(entityAdapter);

    spinner.setOnItemSelectedListener(this);
}

这是我遇到麻烦的地方。 URL_STRING仍为空

public void addURL(View view) {

    if(entity == "Select" && term != null){
        URL_STRING = String.format(getResources().getString(R.string.url1),term);
        SearchDownloader searchDownloader = new SearchDownloader(this);
        searchDownloader.execute();
        listView.setVisibility(View.VISIBLE);
    }else if(term == null){
        Toast.makeText(getApplicationContext(), "Please enter a search term",
                Toast.LENGTH_LONG).show();
    }else{
        URL_STRING = String.format(getResources().getString(R.string.url2), term, entity);
        SearchDownloader searchDownloader = new SearchDownloader(this);
        searchDownloader.execute();
        listView.setVisibility(View.VISIBLE);
    }
}

@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    entity = String.valueOf(spinner.getSelectedItem());
}

@Override
public void onNothingSelected(AdapterView<?> parent) {
    entity = null;
}

}

Answer 1

我不太确定适配器和分配给它的数组。

我已经创建了一些正在寻找的东西，请试试这个，代码可以在Github上找到，如果我可能遗漏了某些内容，请查看它。加载imgae我正在使用名为library的{{1}}，您可以通过将以下代码添加到picasso文件中的依赖项块来轻松导入

build.gradle

你可以使用毕加索

 compile 'com.squareup.picasso:picasso:2.5.2'

activity_spinner_test_two.xml

public class SpinnerTestTwoActivity extends Activity {

    private Spinner url_Spinner;
    private Button load_image_Button;
    private ImageView url_image_ImageView;

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


        initializeUI();
    }

    private void initializeUI() {
        url_Spinner = (Spinner) findViewById(R.id.SpinnerTestTwoActivity_url_spinner);
        load_image_Button = (Button) findViewById(R.id.SpinnerTestTwoActivity_load_image_button);
        url_image_ImageView = (ImageView) findViewById(R.id.SpinnerTestTwoActivity_image_from_url_imageView);

        String[] url_array = getResources().getStringArray(R.array.url_images);

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(getApplicationContext(), R.layout.simple_spinner_dropdown_item, url_array);
        url_Spinner.setAdapter(adapter);

        url_Spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                String image_url = (String)url_Spinner.getItemAtPosition(position);
                Picasso.with(getApplicationContext()).load(image_url).into(url_image_ImageView);
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });
    }

}

url_images

这是您将在<LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:layout_margin="8dp" android:gravity="center" android:orientation="vertical"> <Spinner android:id="@+id/SpinnerTestTwoActivity_url_spinner" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="4dp" /> <Button android:id="@+id/SpinnerTestTwoActivity_load_image_button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_margin="4dp" android:text="Load Image" android:textAllCaps="false" /> <ImageView android:id="@+id/SpinnerTestTwoActivity_image_from_url_imageView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_margin="4dp" android:layout_weight="1" android:scaleType="fitCenter" /> </LinearLayout>目录中的array文件中生成的arrays.xml

res/values

输出

Android：似乎无法使用新值分配变量

1 个答案: