这是我的代码:
public class MainActivity extends AppCompatActivity {
ArrayList<String> nameItems, selectedItems;
ArrayList<Integer> numCheckedArray;
TextView mTextView;
Button mButton;
String[] namesStringArray;
boolean[] checkedItems;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nameItems = new ArrayList();
selectedItems = new ArrayList<>();
numCheckedArray = new ArrayList<>();
nameItems.add("Test 1");
nameItems.add("Test 2");
nameItems.add("Test 3");
nameItems.add("Test 4");
namesStringArray = new String[nameItems.size()];
for (int i =0; i< nameItems.size(); i++){
namesStringArray[i] = nameItems.get(i);
}
checkedItems = new boolean[nameItems.size()];
mButton =(Button)findViewById(R.id.testButton);
mTextView =(TextView)findViewById(R.id.testTextView);
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("Select Your Items");
builder.setMultiChoiceItems(namesStringArray, checkedItems, new DialogInterface.OnMultiChoiceClickListener() {
@Override
public void onClick(DialogInterface dialog, int which, boolean isChecked) {
if (isChecked){
//add the position that the user clicked on
numCheckedArray.add(which);
}else if (numCheckedArray.contains(which)) {
//remove the position that the user clicked on
numCheckedArray.remove(Integer.valueOf(which));
}
}
});
builder.setCancelable(false);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
//add selected items into selected item array still need to figure out how to remove it from the array
for (int i = 0; i < numCheckedArray.size(); i++){
//if item is already in array and is still checked don't do anything
if (selectedItems.contains(nameItems.get(numCheckedArray.get(i))) && checkedItems[numCheckedArray.get(i)] == true){
Log.d("test", "do nothing is called");
}
//if item is already in array and is not checked remove from array
else if (selectedItems.contains(nameItems.get(numCheckedArray.get(i))) && checkedItems[numCheckedArray.get(i)] == false){
Log.d("test", "Remove is called");
selectedItems.remove(nameItems.get(numCheckedArray.get(i)));
}
//add item to array
else {
Log.d("test", "add is called");
selectedItems.add(nameItems.get(numCheckedArray.get(i)));
}
}
//used to see the values of the arrays
for (int i = 0; i < checkedItems.length; i++){
Log.d("test", String.valueOf(checkedItems[i]));
}
for (int i = 0; i < selectedItems.size(); i++){
Log.d("test", selectedItems.get(i));
}
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
AlertDialog dialog = builder.create();
dialog.show();
}
});
}
我想用我的程序完成3个目标。他们是:
当一个项目被选中且不在selectedItems arraylist中时,当我点击确定时将它添加到arraylist(这部分工作正常)。
当一个项目被选中并且已经在selectedItems arraylist中时,当我点击确定时什么都不做(这部分也可以正常工作)。
当一个项目未选中且已经在selectedItems arraylist中时,当我点击确定时将其从arraylist中删除(这部分不起作用并让我疯了)。
我的问题是,为什么永远不会调用以下代码行:
Log.d("test", "Remove is called");
selectedItems.remove(nameItems.get(numCheckedArray.get(i)));
我不明白为什么逻辑在这里不起作用。
谢谢!
答案 0 :(得分:1)
因为您在取消选中项目时删除未经检查的项目(甚至在您按下确定之前)
在这个块中
$00...
因此,当您检查此else if (numCheckedArray.contains(which)) {
//remove the position that the user clicked on
numCheckedArray.remove(Integer.valueOf(which));
}
时,所有项都为真,因为您删除了未选中的
如果您要执行checkedItems[numCheckedArray.get(i)]
评论其他部分Log.d("test", "Remove is called");