Java 按钮setOnClickListener函数调用出现问题
我的代码中的一个按钮的setOnClickListener方法有问题。基本上，我在setOnClickListener方法中调用了一个typeFinder，但是第一次按下按钮时，值不会得到更新。我使用了调试器，根据我的理解，即使调用了该函数，程序实际上也不会执行该函数，直到setOnClickListener之后，这意味着当我第二次按下按钮时，它具有上一次按下按钮时显示的正确值。我也尝试过使用TypesTask（如页面底部的注释部分所示），但这样做的结果是相同的。 下面是该类的代码：Java 按钮setOnClickListener函数调用出现问题,java,android,firebase,firebase-realtime-database,Java,Android,Firebase,Firebase Realtime Database,我的代码中的一个按钮的setOnClickListener方法有问题。基本上，我在setOnClickListener方法中调用了一个typeFinder，但是第一次按下按钮时，值不会得到更新。我使用了调试器，根据我的理解，即使调用了该函数，程序实际上也不会执行该函数，直到setOnClickListener之后，这意味着当我第二次按下按钮时，它具有上一次按下按钮时显示的正确值。我也尝试过使用TypesTask（如页面底部的注释部分所示），但这样做的结果是相同的。 下面是该类的代码： impor
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private DatabaseReference myRef;
private ArrayList<String> recipesList = new ArrayList<String>();
private String[] types = {"pizza", "ice cream", "sandwich", "salad", "steak"};
private void typeFinder(String type) {
myRef.orderByChild("type").equalTo(type).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
String word = "";
boolean wordAdded = false;
String value = dataSnapshot.getValue().toString();
for (int i = 0; i < value.length(); i++) {
if (wordAdded == false) {
if (value.charAt(i) == '=') {
recipesList.add(word);
wordAdded = true;
word = "";
} else if (value.charAt(i) != '{' && value.charAt(i) != ',') {
if (word.length() == 0 && value.charAt(i) == ' ') {
} else {
word = word + value.charAt(i);
}
}
}
if (value.charAt(i) == '}')
if (i + 2 == value.length()) {
wordAdded = false;
break;
} else
wordAdded = false;
}
}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException());
}
});
}
@Override
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_main);
myRef = FirebaseDatabase.getInstance().getReference();
Button saladsB = (Button) findViewById(R.id.saladButton);
Button pizzaB = (Button) findViewById(R.id.pizzaButton);
Button iceCreamB = (Button) findViewById(R.id.iceCreamButton);
Button steakB = (Button) findViewById(R.id.steakButton);
Button sandwichB = (Button) findViewById(R.id.sandwichButton);
final TextView testTextView = (TextView) findViewById(R.id.test_text_view);
testTextView.setText(Integer.toString(recipesList.size()));
super.onCreate(savedInstanceState);
saladsB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// recipesList.clear();
// t.typeFinder("salad")
typeFinder("salad");
// new TypesTask().execute("salad");
String recipes = "";
for (int i = 0; i < recipesList.size(); i++) {
recipes = recipes + recipesList.get(i) + "\n";
}
testTextView.setText(recipes);
// Intent intent = new Intent(MainActivity.this, ListviewActivity.class);
// intent.putStringArrayListExtra("FOOD_LIST", recipesList);
// startActivity(intent);
}
});
}
/*
public class TypesTask extends AsyncTask<String, Void, Void> {
@Override
protected void onPreExecute() {
myRef = FirebaseDatabase.getInstance().getReference();
}
@Override
protected Void doInBackground(String... params) {
typeFinder(params[0]);
return null;
}
}
*/
}
导入android.os.AsyncTask；
导入android.support.v7.app.AppActivity；
导入android.os.Bundle；
导入android.util.Log；
导入android.view.view；
导入android.widget.Button；
导入android.widget.TextView；
导入com.google.firebase.database.DataSnapshot；
导入com.google.firebase.database.DatabaseError；
导入com.google.firebase.database.DatabaseReference；
导入com.google.firebase.database.FirebaseDatabase；
导入com.google.firebase.database.ValueEventListener；
导入java.util.ArrayList；
公共类MainActivity扩展了AppCompatActivity{
私有静态最终字符串TAG=“MainActivity”；
私有数据库参考myRef；
私有ArrayList recipesList=新ArrayList（）；
私有字符串[]类型={“比萨饼”、“冰淇淋”、“三明治”、“沙拉”、“牛排”}；
私有void类型查找器（字符串类型）{
myRef.orderByChild（“类型”）.equalTo（类型）.addValueEventListener（新的ValueEventListener（）{
@凌驾
公共void onDataChange（DataSnapshot DataSnapshot）{
//使用初始值调用此方法一次，然后再次调用
//每当更新此位置的数据时。
字串=”；
boolean-wordAdded=false；
字符串值=dataSnapshot.getValue（）.toString（）；
对于（int i=0；i<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.thevash.recipes.MainActivity">
<LinearLayout
android:layout_width="0dp"
android:layout_height="810dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="458dp"
android:orientation="horizontal"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:layout_constraintLeft_creator="1"
tools:layout_constraintRight_creator="1"
tools:layout_constraintTop_creator="1">
<TextView
android:id="@+id/test_text_view"
android:layout_width="585dp"
android:layout_height="248dp"
android:layout_weight="1"
android:text="TextView"
tools:layout_editor_absoluteX="8dp"
tools:layout_editor_absoluteY="-377dp" />
</LinearLayout>
<Button
android:id="@+id/saladButton"
android:layout_width="0dp"
android:layout_height="48dp"
android:text="Salads"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="5dp"
tools:layout_constraintLeft_creator="1"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/pizzaButton"
android:layout_width="0dp"
android:layout_height="48dp"
android:text="Pizzas"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="52dp"
tools:layout_constraintLeft_creator="1"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/iceCreamButton"
android:layout_width="0dp"
android:layout_height="48dp"
android:text="ice cream"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
app:layout_constraintRight_toRightOf="@+id/pizzaButton"
app:layout_constraintTop_toBottomOf="@+id/pizzaButton"
tools:layout_constraintLeft_creator="1"
app:layout_constraintLeft_toLeftOf="@+id/pizzaButton" />
<Button
android:id="@+id/steakButton"
android:layout_width="0dp"
android:layout_height="48dp"
android:text="steaks"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
app:layout_constraintRight_toRightOf="@+id/iceCreamButton"
app:layout_constraintTop_toBottomOf="@+id/iceCreamButton"
tools:layout_constraintLeft_creator="1"
app:layout_constraintLeft_toLeftOf="@+id/iceCreamButton" />
<Button
android:id="@+id/sandwichButton"
android:layout_width="0dp"
android:layout_height="48dp"
android:text="sandwiches"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
app:layout_constraintRight_toRightOf="@+id/steakButton"
app:layout_constraintTop_toBottomOf="@+id/steakButton"
tools:layout_constraintLeft_creator="1"
app:layout_constraintLeft_toLeftOf="@+id/steakButton" />
</android.support.constraint.ConstraintLayout>
您可以使用TypesTask完成此操作，但需要修改TypesTask类，如下所示
public class TypesTask extends AsyncTask<String, Void, Void> {
@Override
protected void onPreExecute() {
myRef = FirebaseDatabase.getInstance().getReference();
}
@Override
protected Void doInBackground(String... params) {
typeFinder(params[0]);
return null;
}
@Override
onPostExecute(Void result){
String recipes = "";
for (int i = 0; i < recipesList.size(); i++) {
recipes = recipes + recipesList.get(i) + "\n";
}
testTextView.setText(recipes);
}
}
构建reciepeList的方法是异步调用。在调用EventListener的OnSuccess（）之后，需要更新对Ui的更改。将Ui更新代码重新定位到OnDataChange，请参见下面的代码：
private void typeFinder(String type) {
myRef.orderByChild("type").equalTo(type).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
String word = "";
boolean wordAdded = false;
String value = dataSnapshot.getValue().toString();
for (int i = 0; i < value.length(); i++) {
if (wordAdded == false) {
if (value.charAt(i) == '=') {
recipesList.add(word);
wordAdded = true;
word = "";
} else if (value.charAt(i) != '{' && value.charAt(i) != ',') {
if (word.length() == 0 && value.charAt(i) == ' ') {
} else {
word = word + value.charAt(i);
}
}
}
if (value.charAt(i) == '}')
if (i + 2 == value.length()) {
wordAdded = false;
break;
} else
wordAdded = false;
}
// Update the Ui Here
String recipes = "";
for (int i = 0; i < recipesList.size(); i++) {
recipes = recipes + recipesList.get(i) + "\n";
}
this.testTextView.setText(recipes);
}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException());
}
});
}
private void类型查找器（字符串类型）{
myRef.orderByChild（“类型”）.equalTo（类型）.addValueEventListener（新的ValueEventListener（）{
@凌驾
公共void onDataChange（DataSnapshot DataSnapshot）{
//使用初始值调用此方法一次，然后再次调用
//每当更新此位置的数据时。
字串=”；
boolean-wordAdded=false；
字符串值=dataSnapshot.getValue（）.toString（）；
private void typeFinder(String type) {
myRef.orderByChild("type").equalTo(type).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
String word = "";
boolean wordAdded = false;
String value = dataSnapshot.getValue().toString();
for (int i = 0; i < value.length(); i++) {
if (wordAdded == false) {
if (value.charAt(i) == '=') {
recipesList.add(word);
wordAdded = true;
word = "";
} else if (value.charAt(i) != '{' && value.charAt(i) != ',') {
if (word.length() == 0 && value.charAt(i) == ' ') {
} else {
word = word + value.charAt(i);
}
}
}
if (value.charAt(i) == '}')
if (i + 2 == value.length()) {
wordAdded = false;
break;
} else
wordAdded = false;
}
// Update the Ui Here
String recipes = "";
for (int i = 0; i < recipesList.size(); i++) {
recipes = recipes + recipesList.get(i) + "\n";
}
this.testTextView.setText(recipes);
}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException());
}
});
}