下面是我用于Android应用程序开发的3个java类.我想在AddActivity中添加学生数据(姓名和电话号码),点击"添加"后存储在MainActivity页面中.我已经研究过这个并尝试使用数组.但是我对于代码如何将AddActivity中键入的数据发送到MainActivity页面的逻辑非常困惑.任何人都可以给我一个如何解决这个问题的指导,如果你能用另一种方式向我展示我正在尝试的方式,我真的很感激.我希望在AddActivity页面中单击的每个"Add"之后,将数据以ListView格式存储在MainActivity中.我希望有人能指导我这样做.谢谢.
MainActivity.java - https://jsfiddle.net/eb1fprnn/
public class MainActivity extends AppCompatActivity {
ListView listView;
Button addStudent;
ArrayList<Student> students = new ArrayList<Student>();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
add();
}
public void add() {
Student student;
addStudent = (Button) findViewById(R.id.add);
addStudent.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, AddActivity.class);
startActivity(intent);
}
});
}
}
AddActivity.java - https://jsfiddle.net/40k5mas2/
public class AddActivity extends AppCompatActivity {
EditText name, phone;
Button add;
int FphoneNumber;
String Fname;
ArrayList<Student> students;
@Override
protected …在将d3.tip方法添加到代码中之前,将显示条形图.但是,在添加d3.tip方法后,没有显示任何内容,并且此错误显示在控制台中.如何解决此问题并将d3.tip添加到条形图中？未捕获的TypeError:对象#没有方法'tip'
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
font: 10px sans-serif;
}
.y.axisRight text {
fill: orange;
}
.y.axisLeft text {
fill: steelblue;
}
.axis path,
.axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.bar1 {
fill: steelblue;
}
.bar2 {
fill: orange;
}
.x.axis path {
display: black;
}
.d3-tip {
line-height: 1;
font-weight: bold;
padding: 12px;
background: rgba(0, 0, 0, 0.8);
color: #fff;
border-radius: 2px;
}
/* Creates a small triangle extender for the tooltip */ …这是我正在使用的JSON文件，我想使用ysec.domain（[d3.min（data，function（d）} {return（三列“ male”，“ female”和“ both “）}），d3.max（数据，函数（d）{return（” male“，” female“和” both“这三列的最大值）}）））; 无论如何，我是否要将最小值设置为三列中的最小值：“男性”，“女性”和“两者”，这也适用于最大值？
[{"year":"1960","male":"61.7","female":"65.7","both":"63.7","rankmale":"47","rankfemale":"50","rankall":"45"},
{"year":"1970","male":"65.4","female":"70.2","both":"67.7","rankmale":"45","rankfemale":"45","rankall":"44"},
{"year":"1980","male":"68.9","female":"74.2","both":"71.5","rankmale":"33","rankfemale":"36","rankall":"29"},
{"year":"1990","male":"71.9","female":"76.9","both":"74.3","rankmale":"28","rankfemale":"30","rankall":"30"},
{"year":"2000","male":"76.1","female":"80.1","both":"78.1","rankmale":"11","rankfemale":"24","rankall":"15"},
{"year":"2011","male":"80.1","female":"84.6","both":"82.3","rankmale":"6","rankfemale":"8","rankall":"5"}]
假设我有一个阵列
int[] arr = {1, 2, 3, 4, 5, 6}
我必须输入一个基于用户输入的"键"值.
如果数组有任何两个元素总和到我的键值,则返回true值或false值.为什么我的算法仍有问题？我在嵌套循环中存在一些误解吗？有什么帮助吗？
public static boolean checkPair(int[] arr, int key) {
for (int i = 0; i < arr.length; i++) {
for (int j = i + 1; j < arr.length; j++) {
if (arr[i] + arr[j] == key) {
return true;
} else {
return false;
}
}
}
return false;
}
让我们说对于用户输入1,我可以很容易地找到它的平方.(单个数字输入)如何使用递归方法查找平方和(输入多个数字),例如12345应该给出1*1 + 2*2 + 3*3 + 4*4 + 5*5 = 55？对于基本情况,这是num == 1对的吗？从那里,我如何计算后面的后续数字1？
public static int squareSum(int num) {
if (num == 1) {
return num*num;
} else {
return 0;
}
}