Volley的四大请求

public class MainActivity extends AppCompatActivity {    private String url;    private Context context;    private ImageView mImage;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.content_main);        initView();        /**         * Volley三部曲         * 1.创建请求对象         * 2.创建请求队列         * 3.发起请求         */        url = "http://10.0.3.2:8080/json/student.json";        context = this;    }    public void stringRequest(View v) {        //1.创建请求对象        //第2个参数：成功回调接口，第3个参数：失败回调接口        StringRequest request = new StringRequest(url, new Response.Listener() {            //成功调用该方法            @Override            public void onResponse(String s) {                try {                    showToast(s);                    showLog(s);                    JSONObject json = new JSONObject(s);                    String name = json.getString("name");//正式开发不建议使用，当key不存在，空指针                    String name1 = json.optString("name");//正式开发建议使用，当key不存在，返回默认值                    int age = json.optInt("age");                    showLog("age=" + age + ",name=" + name1);                } catch (JSONException e) {                    e.printStackTrace();                }            }        }, new Response.ErrorListener() {            //错误时调用该方法            @Override            public void onErrorResponse(VolleyError volleyError) {                showLog(volleyError.getMessage());            }        });        //2.创建请求队列        RequestQueue queue = Volley.newRequestQueue(context);        //3.发起请求        queue.add(request);    }    //返回json对象    public void jsonObjectRequest(View v) {        //1.        JSONObject jsonObject = null;//调用接口提交的参数,正式开发不使用这种方式提交参数，重写一个方法getPostParams//        jsonObject.put("password", "123456");        JsonObjectRequest request = new JsonObjectRequest(url, jsonObject, new Response.Listener() {            @Override            public void onResponse(JSONObject jsonObject) {                showLog(jsonObject.toString());            }        }, new Response.ErrorListener() {            @Override            public void onErrorResponse(VolleyError volleyError) {                showLog(volleyError.getMessage());            }        }) {            @Override            protected Map getPostParams() throws AuthFailureError {                HashMap params = new HashMap();                params.put("username", "heima26");                params.put("password", "123456");//                return super.getPostParams();                return params;            }            @Override            protected Map getParams() throws AuthFailureError {//                return super.getParams();                HashMap params = new HashMap();                params.put("username", "heima26");                params.put("password", "123456");//                return super.getPostParams();                return params;            }            @Override            public Map getHeaders() throws AuthFailureError {                return super.getHeaders();            }        };        //2.        RequestQueue queue = Volley.newRequestQueue(context);        //3.        queue.add(request);    }    public void jsonArrayRequest(final View v) {        final String arrayUrl = "http://10.0.3.2:8080/json/students.json";        JsonArrayRequest request = new JsonArrayRequest(arrayUrl, new Response.Listener() {            @Override            public void onResponse(JSONArray jsonArray) {                showLog(jsonArray.toString());                //解析json数组                for (int i = 0; i < jsonArray.length(); i++) {                    //获取每一个数组元素                    JSONObject json = jsonArray.optJSONObject(i);                    String name = json.optString("name");                    int age = json.optInt("age");                    showLog("i=" + i + ",name=" + name + ",age=" + age);                }            }        }, new Response.ErrorListener() {            @Override            public void onErrorResponse(VolleyError volleyError) {                showLog("" + volleyError.getMessage());            }        });        RequestQueue queue = Volley.newRequestQueue(context);        queue.add(request);    }    //返回bitmap对象    public void imageRequest(View v){        String imgUrl = "http://10.0.3.2:8080/imgs/sunny.jpg";        int maxWidth = 120;//0表示默认大小        int maxHeight = 120;//0表示默认大小，大于0对图片大图压缩        Bitmap.Config decodeConfig = Bitmap.Config.RGB_565;// 一个像素点占16位，2byte//        Bitmap.Config decodeConfig = Bitmap.Config.ALPHA_8;//一个像素点占8位，1byte//        Bitmap.Config decodeConfig = Bitmap.Config.ARGB_4444;//一个像素点占16位，2byte//        Bitmap.Config decodeConfig = Bitmap.Config.ARGB_8888;//一个像素点占32位，4byte        /**         * 练习：有一张图片 480 * 800，请计算以下不同图片格式占用大小：         * RGB_565  ：480 * 800 * 2 byte = 除以1024=kb         */        //1.创建请求对象        ImageRequest request = new ImageRequest(imgUrl, new Response.Listener() {            @Override            public void onResponse(Bitmap bitmap) {                mImage.setImageBitmap(bitmap);            }        }, maxWidth, maxHeight, decodeConfig, new Response.ErrorListener() {            @Override            public void onErrorResponse(VolleyError volleyError) {                showLog(volleyError.getMessage());            }        });        //2.创建请求队列        RequestQueue queue = Volley.newRequestQueue(context);        //3.发起网络请求        queue.add(request);    }    private void showLog(String msg) {        Log.e("result", "" + msg);    }    private void showToast(String msg) {        Toast.makeText(MainActivity.this, "" + msg, Toast.LENGTH_SHORT).show();    }    private void initView() {        mImage = (ImageView) findViewById(R.id.image);    }}
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