public class MainActivity extends AppCompatActivity {
    private TextView tv_parse;
    private Button btn_parse;
    private String str=null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_parse= (TextView) findViewById(R.id.tv_parse);
        btn_parse= (Button) findViewById(R.id.btn_parse);
        btn_parse.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                /**
                 * 解析json
                 */
                try {
                    JSONObject obj=new JSONObject(str);
                    String name=obj.getString("name");
                    int age=obj.getInt("age");
                    JSONArray array=obj.getJSONArray("friend");
                    String fri="";
                    for (int i = 0; array!=null&&i <array.length() ; i++) {
                     fri=fri+ array.getString(i);
                    }
                    Toast.makeText(MainActivity.this,name+age+fri,Toast.LENGTH_SHORT).show();
                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }
        });

        /**
         * 写入json文件
         */
        JSONObject object=new JSONObject();
        try {
            object.put("name","张三");
            object.put("age",21);
            JSONArray array=new JSONArray();
            array.put("李四");
            array.put("王五");
            object.put("friend",array);
            str=object.toString();
            tv_parse.setText(str);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }