英文:
Pass a callback as a parameter to abstract setOnClickListener in Android
问题
public interface Callback {
void execute(Button button);
}
protected void addClickListener(final Button button, final Callback callback) {
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
callback.execute(button);
}
});
}
protected Callback numberActions(Button button) {
return new Callback() {
@Override
public void execute(Button button) {
String value = button.getText().toString();
setDisplay(value);
}
};
}
protected void setDisplay(String value) {
String newValue;
displayValue = resultDisplay.getText().toString();
if (displayValue.length() < 10) {
newValue = resultDisplay.getText() + value;
resultDisplay.setText(newValue);
displayValue = newValue;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button numberButtons[] = new Button[11];
numberButtons[0] = (Button) findViewById(R.id.numberOne);
numberButtons[1] = (Button) findViewById(R.id.numberTwo);
numberButtons[2] = (Button) findViewById(R.id.numberTwo);
numberButtons[3] = (Button) findViewById(R.id.numberThree);
numberButtons[4] = (Button) findViewById(R.id.numberFour);
numberButtons[5] = (Button) findViewById(R.id.numberFive);
numberButtons[6] = (Button) findViewById(R.id.numberSix);
numberButtons[7] = (Button) findViewById(R.id.numberSeven);
numberButtons[8] = (Button) findViewById(R.id.numberEight);
numberButtons[9] = (Button) findViewById(R.id.numberNine);
numberButtons[10] = (Button) findViewById(R.id.numberZero);
resultDisplay = (TextView) findViewById(R.id.resultDisplay);
for (Button button : numberButtons) {
addClickListener(button, numberActions(button));
}
}
(Note: I've corrected the duplication in numbering the buttons, and I've added the missing return statement in the numberActions method by creating an anonymous class implementing the Callback interface.)
英文:
public interface Callback {
void execute(Button button);
}
protected void addClickListener(final Button button, final Callback callback) {
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
callback.execute(button);
}
});
}
protected Callback numberActions(Button button) {
String value = button.getText().toString();
setDisplay(value);
}
protected void setDisplay (String value) {
String newValue;
displayValue = resultDisplay.getText().toString();
if (displayValue.length() < 10){
newValue = resultDisplay.getText() + value;
resultDisplay.setText(newValue);
displayValue = newValue;
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button numberButtons[] = new Button[11];
numberButtons[0] = (Button) findViewById(R.id.numberOne);
numberButtons[1] = (Button) findViewById(R.id.numberTwo);
numberButtons[2] = (Button) findViewById(R.id.numberTwo);
numberButtons[3] = (Button) findViewById(R.id.numberThree);
numberButtons[4] = (Button) findViewById(R.id.numberFour);
numberButtons[5] = (Button) findViewById(R.id.numberFive);
numberButtons[6] = (Button) findViewById(R.id.numberSix);
numberButtons[7] = (Button) findViewById(R.id.numberSeven);
numberButtons[8] = (Button) findViewById(R.id.numberEight);
numberButtons[9] = (Button) findViewById(R.id.numberNine);
numberButtons[10] = (Button) findViewById(R.id.numberZero);
resultDisplay = (TextView) findViewById(R.id.resultDisplay);
for (Button button: numberButtons) {
addClickListener(button, numberActions(button));
}
}
I'm building a simple calculator on Android Studio with Java.
Instead of calling setOnClickListener to each instance of a button, I have created addClickListiner to abstract it. So for example, I create an array of number buttons and on the onClick function I define that they should change Input display as an action. My goal is to use addClickListener to each button, then I can pass an action as a second parameter (callback) which will define what action that button will perform.
Actually I'm a javascript developer, and that would be as simple as just passing a function as a parameter. As I'm learning Java, I don't know how to perform it... My goal is to pass a void function as a parameter to perform it whenever the button is clicked.
I have tried to create a public interface... But when I try to build it, it breaks saying that I should have a return statement on numberActions method. Can anyone help me with how to pass a callback function as params on this case?
答案1
得分: 0
你可以尝试这样做：
for (Button button : numberButtons) {
button.setOnClickListener(this);
}
实现View.OnClickListener接口。然后在你的activity/fragment中：
@Override
public void onClick(View v) {
Button button = (Button) v;
switch (v.getId()) {
case R.id.numberOne:
String value = button.getText().toString();
setDisplay(value);
break;
}
}
英文:
You can try this
for (Button button : numberButtons) {
button.setOnClickListener = this;
}
Implement the View.OnClickListener interface. Then in your activity/fragment
@Override
public void onClick(View v) {
Button button= (Button) v
switch(v.getId()){
case R.id.numberOne:
String value = button.getText().toString();
setDisplay(value);
break;
}
}
答案2
得分: 0
// 使用一个 Consumer<Button> 作为回调函数，以便在按钮被点击时执行相应操作
您可以通过使用 [`Consumer<Button>`][1] 作为回调来实现这一目标。如果您有一些动作按钮（例如 "+"、"-"）以及带有数字的按钮，那么您的 `numberActions()` 方法可以按照以下方式工作：
```java
private Consumer<Button> add = new Consumer<Button>() {
@Override
public void accept(Button button) {
Toast.makeText(MainActivity.this, "'Add' 尚未实现", Toast.LENGTH_SHORT).show();
}
};
private Consumer<Button> subtract = new Consumer<Button>() {
@Override
public void accept(Button button) {
Toast.makeText(MainActivity.this, "'Subtract' 尚未实现", Toast.LENGTH_SHORT).show();
}
};
protected Consumer<Button> numberActions(Button button) {
final String value = button.getText().toString();
switch (value){
case "+":
return add;
case "-":
return subtract;
default: // 必须是数字
return new Consumer<Button>(){
@Override
public void accept(Button button) {
setDisplay(value);
}
};
}
}
<details>
<summary>英文:</summary>
>My goal is to pass a void function as a parameter to perform it whenever the button is clicked
You can achieve this by using a [`Consumer<Button>`][1] as callback. If you have some action buttons (e.g. "+", "-") as well as buttons with digits then your method `numberActions()` could work like this:
private Consumer<Button> add = new Consumer<Button>() {
@Override
public void accept(Button button) {
Toast.makeText(MainActivity.this, "'Add' not yet implemented", Toast.LENGTH_SHORT).show();
}
};
private Consumer<Button> subtract = new Consumer<Button>() {
@Override
public void accept(Button button) {
Toast.makeText(MainActivity.this, "'Subtract' not yet implemented", Toast.LENGTH_SHORT).show();
}
};
protected Consumer<Button> numberActions(Button button) {
final String value = button.getText().toString();
switch (value){
case "+":
return add;
case "-":
return subtract;
default: // must be a digit
return new Consumer<Button>(){
@Override
public void accept(Button button) {
setDisplay(value);
}
};
}
}
[1]: https://developer.android.com/reference/androidx/core/util/Consumer
</details>
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