我基本上是一个初学者 Android 开发人员,正在努力从我正在使用的 linkedList 中删除项目。我无法工作的功能是“deleteLast()”,任何帮助将不胜感激。我也可能可以完成相当多的修复,但主要问题是前面提到的问题。
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.InputType;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private EditText problemView;
private String problem;
private TextView answerView;
int cursorPosition = 0;
List<String> operationsList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//initialising views
problemView = (EditText) findViewById(R.id.problemView);
answerView = (TextView) findViewById(R.id.answerView);
//prevents an underline appearing in the editText
problemView.setInputType(InputType.TYPE_TEXT_FLAG_NO_SUGGESTIONS|InputType.TYPE_NULL);
//initialise the the linkedList for the data structure
operationsList = new LinkedList<>();
problem = "";
//create numerical buttons
Button button0 = (Button) findViewById(R.id.button0);
Button button1 = (Button) findViewById(R.id.button1);
Button button2 = (Button) findViewById(R.id.button2);
Button button3 = (Button) findViewById(R.id.button3);
Button button4 = (Button) findViewById(R.id.button4);
Button button5 = (Button) findViewById(R.id.button5);
Button button6 = (Button) findViewById(R.id.button6);
Button button7 = (Button) findViewById(R.id.button7);
Button button8 = (Button) findViewById(R.id.button8);
Button button9 = (Button) findViewById(R.id.button9);
//create symbolic buttons
Button buttonDivide = (Button) findViewById(R.id.buttonDivide);
Button buttonMultiply = (Button) findViewById(R.id.buttonMultiply);
Button buttonAddition = (Button) findViewById(R.id.buttonAddition);
Button buttonSubtract = (Button) findViewById(R.id.buttonSubtract);
Button buttonPoint = (Button) findViewById(R.id.buttonPoint);
Button buttonScientificNotation = (Button) findViewById(R.id.buttonScientificNotation);
Button buttonAnswer = (Button) findViewById(R.id.buttonAnswer);
//create non-displaying buttons
Button buttonClearAll = (Button) findViewById(R.id.buttonClearAll);
Button buttonDelete = (Button) findViewById(R.id.buttonDelete);
Button buttonEquals = (Button) findViewById(R.id.buttonEquals);
//onClickListener for showable buttons, numbers, signs etc.
View.OnClickListener listener = new View.OnClickListener() {
@Override
public void onClick(View view) {
Button b = (Button) view;
String value = b.getText().toString();
operationsList.add(problemView.getSelectionStart(), value);
// problem += b.getText().toString();
cursorPosition = problemView.getSelectionStart() + 1;
displayArray();
}
};
// //onClickListener for scientific notation button since need to advance cursor more
// View.OnClickListener listenerScientific = new View.OnClickListener() {
// @Override
// public void onClick(View view) {
// Button b = (Button) view;
// String value = b.getText().toString();
//
// operationsList.add(problemView.getSelectionStart(), value);
//// problem += b.getText().toString();
// cursorPosition = problemView.getSelectionStart() + 1;
// displayArray();
// }
// };
button0.setOnClickListener(listener);
button1.setOnClickListener(listener);
button2.setOnClickListener(listener);
button3.setOnClickListener(listener);
button4.setOnClickListener(listener);
button5.setOnClickListener(listener);
button6.setOnClickListener(listener);
button7.setOnClickListener(listener);
button8.setOnClickListener(listener);
button9.setOnClickListener(listener);
buttonDivide.setOnClickListener(listener);
buttonMultiply.setOnClickListener(listener);
buttonAddition.setOnClickListener(listener);
buttonSubtract.setOnClickListener(listener);
buttonPoint.setOnClickListener(listener);
buttonScientificNotation.setOnClickListener(listener);
buttonAnswer.setOnClickListener(listener);
View.OnClickListener nonListener = new View.OnClickListener() {
@Override
public void onClick(View view) {
if (view.getId() == R.id.buttonClearAll){
clearAll();
displayArray();
}
if (view.getId() == R.id.buttonDelete){
deleteLast();
}
if (view.getId() == R.id.buttonEquals){
}
}
};
buttonClearAll.setOnClickListener(nonListener);
buttonDelete.setOnClickListener(nonListener);
buttonEquals.setOnClickListener(nonListener);
}
public void displayArray(){
Iterator<String> iterator = operationsList.listIterator();
String temp = "";
while (iterator.hasNext()){
temp += iterator.next();
}
problemView.setText(temp);
problemView.setSelection(cursorPosition);
}
// public boolean delete(){
// stringProblemArray[spaceUsed-1] = null;
// spaceUsed -= 1;
// problemView.setSelection(problemView.getSelectionStart() - 1);
// return true;
// }
//
public void clearAll(){
operationsList.clear();
cursorPosition = 0;
}
public void deleteLast(){
Iterator<String> iterator = operationsList.listIterator();
int index = 0;
while (iterator.hasNext()){
if (index == cursorPosition-1){
iterator.remove();
}else {
iterator.next();
}
}
displayArray();
// if (iterator.hasNext()){
// for (int i =0; i == cursorPosition; i++){
// iterator.next();
// }
// iterator.remove();
// }
// for(Iterator<String> iter = operationsList.iterator(); iter.hasNext();) {
// String data = iter.next();
// if ( == rec1) {
// iter.remove();
// }
// }
}
}
最佳答案
LinkedList
已经有 removeLast()
方法,不用写你的,直接写
operationsList.removeLast()
仅此而已。
此外,如果您不想将列表转换为 LinkedList(即使您实际上正在使用 LinkedList),您可以使用索引删除最后一个元素
operationsList.remove(operationsList.size()-1);
关于java - 从android中的linikedList中删除项目,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45141379/