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android - 获取“尝试获取空数组的长度”错误

问题描述

我收到“尝试获取空数组的长度”错误。当我尝试单击按钮时，我试图从链接https://gturnquist-quoters.cfapps.io/api/random获取随机引号：键入“成功”值
id 7 引用“引导的真正好处，但是，它只是 Spring。这意味着代码采用的任何方向，无论复杂性如何，我都知道这是一个安全的选择。

MainActivity.java

public class MainActivity extends AppCompatActivity {

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


        btnCallRestApi = findViewById(R.id.btnCallRestApi);
        btnCallRestApi.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //call Rest Api
                new HttpReqTask().execute();

            }
        });
    }
    private class HttpReqTask extends AsyncTask<Void, Void, Value[]> {
        @Override
        protected Value[] doInBackground(Void... params){
            try{
                String apiUrl = "https://gturnquist-quoters.cfapps.io/api/random";
                RestTemplate rest = new RestTemplate();
                rest.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
                Value[] quotes = rest.getForObject(apiUrl, Value[].class);
                return quotes;
            }catch (Exception ex){
                Log.e("Could not get Quotes",ex.getMessage());
            }
            return null;
        }
        protected void onPostExecute(Value[] quotes){
            super.onPostExecute(quotes);
            for(Value v:quotes){
                Log.i("id: ", String.valueOf(v.getId()));
                Log.i("quote: ", v.getQuote());
            }
        }
    }
}

引用.java

 public Quote() {
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public Value getValue() {
        return value;
    }

    public void setValue(Value value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Quote{" +
                "type='" + type + '\'' +
                ", value=" + value +
                '}';
    }

价值.java

 public Value() {
    }

    public Long getId() {
        return this.id;
    }

    public String getQuote() {
        return this.quote;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public void setQuote(String quote) {
        this.quote = quote;
    }

    @Override
    public String toString() {
        return "Value{" +
                "id=" + id +
                ", quote='" + quote + '\'' +
                '}';
    }

标签： androidrest

解决方案

您正在尝试对触发 a 的空数组执行循环NPE，尝试使用try/catch子句处理它

 protected void onPostExecute(Value[] quotes){
            super.onPostExecute(quotes);   
    try {
        for(Value v:quotes){
            Log.i("id: ", String.valueOf(v.getId()));
            Log.i("quote: ", v.getQuote());
        }
    } catch (NullPointerException e) {
        System.out.print("Caught the NullPointerException");
    }

编辑新问题：

我认为您错误地阅读了 JSON OBJECT ！

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