如何转换一个arraylist<string> 至 arrayList<integer> 并计算其上的整数值？</integer></string>

Question

我应该如何将 ArrayList 字符串从 Listview 值计算为 ArrayList Integer 并返回 Listview，因为我一直在申请 Android 计算来自 ArrayList 的 Listview 项目。这是最让我烦恼的一个，它将最后的 arrayList 值显示为 textView，而不是计算它们

public class Menu extends AppCompatActivity {

public FloatingActionButton fab1, fab2, fab3;
public Animation fab_open, fab_close, rotate_cw, rotate_ccw;
public EditText editText, editText2, editText3, editText4;
public TextView textView1;
public ListView listView;
public ArrayList<String> arrayList;
public ArrayAdapter<String> arrayAdapter;
public boolean isOpen = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_menu);
    fab1 = findViewById(R.id.fab_1);
    fab2 = findViewById(R.id.fab_2);
    fab3 = findViewById(R.id.fab_3);
    textView1 = findViewById(R.id.info_text4);
    listView = findViewById(R.id.listview_items);
    fab_open = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fab_open);
    fab_close = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fab_close);
    rotate_cw = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.rotate_cw);
    rotate_ccw = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.rotate_ccw);
    loadData();
    calculate();
    arrayAdapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_list_item_1, arrayList);
    listView.setAdapter(arrayAdapter);
    fab1.setOnClickListener(view -> {
        if (isOpen) {
            fab2.startAnimation(fab_close);
            fab3.startAnimation(fab_close);
            fab1.startAnimation(rotate_cw);
            fab2.setClickable(true);
            fab3.setClickable(true);
            isOpen = false;
        } else {
            fab2.startAnimation(fab_open);
            fab3.startAnimation(fab_open);
            fab1.startAnimation(rotate_ccw);
            fab2.setClickable(true);
            fab3.setClickable(true);
            isOpen = true;
        }
    });
    // Budget
    fab2.setOnClickListener(view -> {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Add Budget");
        builder.setIcon(R.drawable.ic_wallet_budget);
        final View customLayout = getLayoutInflater().inflate(R.layout.add_budget_popup, null);
        builder.setView(customLayout);
        builder.setPositiveButton("OK", (dialog, which) -> {
            // Budget Name
            editText = customLayout.findViewById(R.id.editText);
            // Budget Input
            editText2 = customLayout.findViewById(R.id.editText2);
            // Conditional Statements
            if(TextUtils.isEmpty(editText.getText().toString()) && TextUtils.isEmpty(editText2.getText().toString())) {
                Toast toast = Toast.makeText(getApplicationContext(), "No Budget Name Data and No Budget Data been added", Toast.LENGTH_SHORT);
                toast.show();
            } else if(TextUtils.isGraphic(editText.getText().toString()) && TextUtils.isEmpty(editText2.getText().toString())){
                Toast toast = Toast.makeText(getApplicationContext(), "Budget Name Data has a input, but No Budget Data input", Toast.LENGTH_SHORT);
                toast.show();
            } else if(TextUtils.isEmpty(editText.getText().toString()) && TextUtils.isDigitsOnly(editText2.getText().toString())){
                Toast toast = Toast.makeText(getApplicationContext(), "Budget Data input has a input, but No Budget Name Data input", Toast.LENGTH_SHORT);
                toast.show();
            } else {
                arrayList.add(editText2.getText().toString());
                arrayAdapter.notifyDataSetChanged();
                Toast toast = Toast.makeText(getApplicationContext(), "Budget Data Added", Toast.LENGTH_SHORT);
                toast.show();
                saveData();
            }
        });
        AlertDialog dialog = builder.create();
        dialog.show();
        dialog.setCancelable(false);
    });
    // Expense
    fab3.setOnClickListener(view -> {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Add Expense");
        builder.setIcon(R.drawable.ic_money_exp);
        final View customLayout = getLayoutInflater().inflate(R.layout.add_expense_popup, null);
        builder.setView(customLayout);
        builder.setPositiveButton("OK", (dialog, which) -> {
            // Expense Name
            editText3 = customLayout.findViewById(R.id.editText3);
            // Expense Input
            editText4 = customLayout.findViewById(R.id.editText4);
            // Conditional Statements
            if(TextUtils.isEmpty(editText3.getText().toString()) && TextUtils.isEmpty(editText4.getText().toString())) {
                Toast toast = Toast.makeText(getApplicationContext(), "No Expense Name Data and No Expense Data been added", Toast.LENGTH_SHORT);
                toast.show();
            } else if(TextUtils.isGraphic(editText3.getText().toString()) && TextUtils.isEmpty(editText4.getText().toString())){
                Toast toast = Toast.makeText(getApplicationContext(), "Expense Name Data has a input, but No Expense Data input", Toast.LENGTH_SHORT);
                toast.show();
            } else if(TextUtils.isEmpty(editText3.getText().toString()) && TextUtils.isDigitsOnly(editText4.getText().toString())){
                Toast toast = Toast.makeText(getApplicationContext(), "Expense Data input has a input, but No Expense Name Data input", Toast.LENGTH_SHORT);
                toast.show();
            } else {
                arrayList.add(editText4.getText().toString());
                arrayAdapter.notifyDataSetChanged();
                Toast toast = Toast.makeText(getApplicationContext(), "Expense Data Added", Toast.LENGTH_SHORT);
                toast.show();
                saveData();
            }
        });
        AlertDialog dialog = builder.create();
        dialog.show();
        dialog.setCancelable(false);
    });
}
private void saveData() {
    SharedPreferences sharedPreferences = getSharedPreferences("SHAREDPREFS", MODE_PRIVATE);
    SharedPreferences.Editor editor = sharedPreferences.edit();
    Gson gson = new Gson();
    String json = gson.toJson(arrayList);
    editor.putString("Test", json);
    editor.apply();

}
private void loadData(){
    SharedPreferences sharedPreferences =  getSharedPreferences("SHAREDPREFS", MODE_PRIVATE);
    Gson gson =  new Gson();
    String json = sharedPreferences.getString("Test", null);
    Type type = new TypeToken<ArrayList<String>>(){}.getType();
    arrayList = gson.fromJson(json, type);
    if(arrayList == null){
        arrayList = new ArrayList<>();
    }
}

private void calculate(){
    for (int i = 0; i < arrayList.size(); i++) {
        textView1.setText(String.valueOf(arrayList.get(i)));
    }
}

@Override
public boolean onCreateOptionsMenu(android.view.Menu menu){
    getMenuInflater().inflate(R.menu.list, menu);
    return true;
}

@SuppressLint("NonConstantResourceId")
@Override
public boolean onOptionsItemSelected(MenuItem items){
    switch (items.getItemId()){
        case R.id.items:
            // Email Feedback System
            Intent intent=new Intent(Intent.ACTION_SEND);
            String[] recipients={"companyenode@gmail.com"};
            intent.putExtra(Intent.EXTRA_EMAIL, recipients);
            intent.putExtra(Intent.EXTRA_SUBJECT,"Subject text here...");
            intent.putExtra(Intent.EXTRA_TEXT,"Body of the content here...");
            intent.putExtra(Intent.EXTRA_CC,"mailcc@gmail.com");
            intent.setType("text/html");
            intent.setPackage("com.google.android.gm");
            startActivity(Intent.createChooser(intent, "Send mail"));
        case R.id.items3:
            // About App
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setTitle("About");
            builder.setIcon(R.drawable.ic_baseline_info_24);
            builder.setMessage("Our app allows you to monitor and categorize your expenses across different bank and investment accounts and credit cards, our app also offer budgeting tools, credit monitoring, mileage tracking, receipt keeping, and advice to grow your net worth.");
            builder.setCancelable(false);
            builder.setPositiveButton("Close", (dialog, id) -> dialog.cancel());
            AlertDialog alert = builder.create();
            alert.show();
        default:
            return super.onOptionsItemSelected(items);
    }
}

@Override
public void onBackPressed() {
    new AlertDialog.Builder(this).
            setIcon(android.R.drawable.ic_dialog_alert)
            .setTitle("Exit")
            .setMessage("Are you sure you want to close app?")
            .setPositiveButton("Yes", (dialog, which) -> finish())
            .setNegativeButton("No", null)
            .show();
}

}

那是我的问题，我的代码有问题吗？

Answer 1

问题出在这个function

private void calculate(){
    for (int i = 0; i < arrayList.size(); i++) {
        textView1.setText(String.valueOf(arrayList.get(i)));
    }
}

您正在遍历数组列表并按顺序将文本设置为每个数组列表条目。 这意味着它将覆盖之前的任何文本并最终只显示最后一个条目。 如果您的数组列表是["1","2","3"]这与调用相同

testView1.setText("1");
testView1.setText("2"); // overrides the "1"
testView1.setText("3"); // overrides the "2"
// ends with it showing "3"

如果你想显示所有数组条目的总和，你应该首先计算总和，然后显示它，如下所示：

private void calculate() {
    // first calculate the total
    int total = 0;
    for (int i = 0; i < arrayList.size(); i++) {
        total += Integer.parseInt(arrayList.get(i));
    }

    // then display it
    textView1.setText(String.valueOf(total));
}

如果数组列表中的任何数字不是整数，当您调用parseInt时，这将抛出NumberFormatException ，因此如果有可能，您应该添加一些异常处理

private void calculate() {
    int total = 0;
    for (int i = 0; i < arrayList.size(); i++) {
        try {
            total += Integer.parseInt(arrayList.get(i));
        } catch( NumberFormatException e) {
            e.printStackTrace();
        }
    }
    textView1.setText(String.valueOf(total));
}