我着手创建一个包含3个活动的Android应用程序项目。
第一个活动的布局包含3个元素，2个微调器和一个按钮。
我打算使它们以以下方式工作：
MainActivity.java：1.假设我希望第一个微调器在应用程序启动时加载一组类别。例如收入，支出。2.从第一个微调器中选择一个类别后，第二个微调器将在第二个微调器中加载其各自的子类别。例如，如果我在第一个微调器中选择“收入”，则第二个微调器带有佣金，薪金，奖金等费用，并且如果选择“支出”，则在第二个微调器中装入“每月支出”，“运输性”，“账单”等。3.现在，根据我选择的子类别，当我单击按钮时，它将打开一个新活动，并为该特定类别和子类别设置操作栏的标题。例如，如果我选择收入和薪水，则在单击主活动中的按钮后，下一个活动将显示收入，薪水作为标题。
我创建了一个名为Utils.java的类，用于将类别和子类别名称集存储为字符串数组。
public class Utils{
public static String[] mainCategoryList =
{
"Choose One",
"Income",
"Expenditure"
};
//
public static String[] chooseOne_list=
{
"Choose One"
};
public static String[] income_subCategoryList =
{
"Bonus",
"Commision",
"Salary"
};
public static String[] expenditure_subCategoryList=
{
"Bills",
"Conveyance",
"Monthly Expenditure"
};
public static String[] income=
{
"Income, Bonus",
"Income, Commission",
"Income, Salary"
};
public static String[] expenditure=
{
"Expenditure, Bills",
"Expenditure, Conveyance",
"Expenditure, Monthly Expenditure"
};
}
我为MainActivity.java完成的编码如下所示，
public class MainActivity extends AppCompatActivity {
Spinner spinner1_mainCategory, spinner2_subCategory;
Button buttonChoose;
String spinner1Item, spinner2Item;
Intent intent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Spinner element
spinner1_mainCategory = (Spinner)findViewById(R.id.spinner1_mainCategory);
spinner2_subCategory = (Spinner)findViewById(R.id.spinner2_subCategory);
//Button element
buttonChoose = (Button)findViewById(R.id.buttonChoose);
//To keep onCreate() clean of multiple adapter setting
adapterMethod(spinner1_mainCategory,mainCategoryList);
// Spinner click listener
spinner1_mainCategory.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int position, long id) {
//String.valueOf(array_name.getSelectedItem()) captures the value of the selected option of a specific string array onClick event
spinner1Item = String.valueOf(spinner1_mainCategory.getSelectedItem());
switch (position){
case 0:
adapterMethod(spinner2_subCategory,chooseOne_list);
spinner2_subCategory.setVisibility(View.GONE);
//Button click listener
buttonChoose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (spinner1Item.contentEquals(Utils.mainCategoryList[0])){
Toast toast = Toast.makeText(getApplicationContext(), "Choose a Category First", Toast.LENGTH_SHORT);
toast.setGravity(Gravity.CENTER|Gravity.CENTER_HORIZONTAL,0,0);
toast.show();
}
}
});
break;
case 1:
adapterMethod(spinner2_subCategory,income_subCategoryList);
spinner2_subCategory.setVisibility(View.VISIBLE);
break;
case 2:
adapterMethod(spinner2_subCategory,expenditure_subCategoryList);
spinner2_subCategory.setVisibility(View.VISIBLE);
break;
}
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
spinner2_subCategory.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, final int position, long id) {
spinner2Item = String.valueOf(spinner2_subCategory.getSelectedItem());
switch (position){
case 0:
//Income Category, Bonus Sub-category
if (spinner2Item.contentEquals(Utils.mainCategoryList[1]) && spinner2Item.contentEquals(income_subCategoryList[0])){
buttonChoose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
changeTitleInNextActivity(Utils.income[0]);
}
});
}
//Expenditure Category, Bills Sub-category
if (spinner2Item.contentEquals(Utils.mainCategoryList[2]) && spinner2Item.contentEquals(expenditure_subCategoryList[0])){
buttonChoose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
changeTitleInNextActivity(Utils.expenditure[0]);
}
});
}
break;
case 1:
//Income Category, Commission Sub-category
if (spinner2Item.contentEquals(Utils.mainCategoryList[1]) && spinner2Item.contentEquals(income_subCategoryList[1])){
buttonChoose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
changeTitleInNextActivity(Utils.income[1]);
}
});
}
//Expenditure Category, Conveyance Sub-category
if (spinner2Item.contentEquals(Utils.mainCategoryList[2]) && spinner2Item.contentEquals(expenditure_subCategoryList[1])){
buttonChoose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
changeTitleInNextActivity(Utils.expenditure[1]);
}
});
}
break;
case 2:
//Income Category, Salary Sub-category
if (spinner2Item.contentEquals(Utils.mainCategoryList[1]) && spinner2Item.contentEquals(income_subCategoryList[2])){
buttonChoose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
changeTitleInNextActivity(Utils.income[2]);
}
});
}
//Expenditure Category, Monthly Expenditure Sub-category
if (spinner2Item.contentEquals(Utils.mainCategoryList[2]) && spinner2Item.contentEquals(expenditure_subCategoryList[2])){
buttonChoose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
changeTitleInNextActivity(Utils.expenditure[2]);
}
});
}
break;
}
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
}
public void adapterMethod(View v, String[] list){
// Creating adapter for spinner
ArrayAdapter<String> dataAdapter = new ArrayAdapter<>(this,
android.R.layout.simple_spinner_item, list);
// Drop down layout style - list view with radio button
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
dataAdapter.notifyDataSetChanged();
// attaching adapter to spinner for district
if (v.getId()==R.id.spinner1_mainCategory){
spinner1_mainCategory.setAdapter(dataAdapter);
spinner1_mainCategory.setSelection(0, false);
}
if (v.getId()==R.id.spinner2_subCategory){
spinner2_subCategory.setAdapter(dataAdapter);
spinner2_subCategory.setSelection(0, false);
}
}
public void changeTitleInNextActivity(String title){
intent = new Intent(getApplicationContext(),SecondActivity.class);
intent.putExtra("Title", title);
startActivity(intent);
}
}
SecondActivity.java
public class SecondActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
Intent intent = getIntent();
String title = intent.getStringExtra("Title");
getSupportActionBar().setTitle(title);
}
}
我不明白为什么，但是我无法让编码按我想要的方式为我工作。从第一个和第二个微调器中进行选择可以完美地工作，但是无论我尝试了多少种方法，都无法使用它来设置下一个活动中的标题的按钮。
告诉我，伙计们，我做错了什么？如何更好地编写代码以避免这种陷阱。
无法使按钮“选择”：
在第二个活动中，获取您传递的字符串
String title=getIntent().getStringExtra("Title");
然后设置你的标题
getSupportActionBar().setTitle(title);
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我来说两句