Question

每次服务器使用android volley或任何其他库发送新的JSON对象时，如何自动（无任何按钮）更新textview？这是一个仅具有一个文本视图的简单程序。我已经粘贴了两个文件。每当我从服务器端输入文本并希望它们立即显示在textview中时，我都会获取JSON文件。

mainactivity.java

    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.widget.TextView;

    import com.android.volley.Request;
    import com.android.volley.RequestQueue;
    import com.android.volley.Response;
    import com.android.volley.VolleyError;
    import com.android.volley.toolbox.JsonObjectRequest;
    import com.android.volley.toolbox.Volley;
    import org.json.JSONException;
    import org.json.JSONObject;


    public class MainActivity extends AppCompatActivity {
    // Will show the string "data" that holds the results
    TextView results;
    // URL of object to be parsed
    String JsonURL = "url_link";
    // This string will hold the results
    String data = "";
    // Defining the Volley request queue that handles the URL request concurrently
    RequestQueue requestQueue;

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


        // Creates the Volley request queue
        requestQueue = Volley.newRequestQueue(this);

        // Casts results into the TextView found within the main layout XML with id jsonData
        results = (TextView) findViewById(R.id.jsonData);
        JSONObject jsonObj = new JSONObject();


        // Creating the JsonObjectRequest class called obreq, passing required parameters:
        //GET is used to fetch data from the server, JsonURL is the URL to be fetched from.
        JsonObjectRequest obreq = new JsonObjectRequest(Request.Method.GET, JsonURL, jsonObj, new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {
                        try {
                            JSONObject obj = response.getJSONObject("colorObject");

                            String color = obj.getString("colorName");
                         //   String desc = obj.getString("description");

                            data += "Color Name: " + color;

                            // Adds the data string to the TextView "results"
                            results.setText(data);
                        }
                        // Try and catch are included to handle any errors due to JSON
                        catch (JSONException e) {
                            // If an error occurs, this prints the error to the log
                            e.printStackTrace();
                        }
                    }
                }, new Response.ErrorListener() {
                    @Override
                    // Handles errors that occur due to Volley
                    public void onErrorResponse(VolleyError error) {
                        Log.e("Volley", "Error");
                    }
                }
        );
        // Adds the JSON object request "obreq" to the request queue
        requestQueue.add(obreq);
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
tools:context=".MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="Large Text"
    android:textSize="20sp"
    android:textStyle="bold"
    android:id="@+id/jsonData"
    android:textColor="#000000" />

</ScrollView>

Answer 1

您可以使用警报管理器。可以将警报管理器设置为在将来的特定时间执行某项操作，例如在15:30或每隔一分钟（例如）。根据{{3}}：

此类可访问系统警报服务。这些使您可以安排应用程序在未来

使用Volley更新Android中的textview

1 个答案: