在Android Studio中找不到符号错误 [英] Cannot find symbol error in android studio
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问题描述
我正在尝试将片段添加到导航抽屉中.但是我有一个错误:找不到符号类Fragment.
I'm trying to add fragments to a navigation drawer. But I have the error: cannot find symbol class Fragment.
我添加了:import android.support.v4.app.Fragment
I added: import android.support.v4.app.Fragment
还添加片段对象(片段片段)
Also add the fragment object(Fragment fragment)
错误在哪里? 我该怎么办?
Where is the mistake? What should I do?
Home.java
Home.java
package com.example.eatit;
import android.os.Bundle;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import android.view.View;
import androidx.core.view.GravityCompat;
import androidx.appcompat.app.ActionBarDrawerToggle;
import android.view.MenuItem;
import com.google.android.material.navigation.NavigationView;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.view.Menu;
import android.support.v4.app.Fragment;
public class Home extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
Fragment fragment = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.home, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
/* Handle navigation view item clicks here. */
int id = item.getItemId();
if (id == R.id.nav_home) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_tools) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
build.grandle
build.grandle
apply plugin: 'com.android.application'
android {
compileSdkVersion 29
buildToolsVersion "29.0.0"
defaultConfig {
applicationId "com.example.eatit"
minSdkVersion 16
targetSdkVersion 29
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
vectorDrawables.useSupportLibrary = true
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'androidx.appcompat:appcompat:1.0.2'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'com.google.firebase:firebase-database:16.0.4'
implementation 'androidx.legacy:legacy-support-v4:1.0.0'
implementation 'com.google.android.material:material:1.0.0'
testİmplementation 'junit:junit:4.12'
androidTestİmplementation 'androidx.test:runner:1.2.0'
androidTestİmplementation 'androidx.test.espresso:espresso-core:3.2.0'
implementation 'com.google.firebase:firebase-core:17.0.0'
implementation 'com.google.firebase:firebase-core:10.2.0'
implementation 'com.google.firebase:firebase-database:17.0.0'
implementation 'info.hoang8f:fbutton:1.0.5'
implementation 'com.rengwuxian.materialedittext:library:2.1.4'
implementation 'androidx.cardview:cardview:1.0.0'
implementation 'androidx.recyclerview:recyclerview:1.0.0'
implementation 'com.squareup.picasso:picasso:2.5.2'
implementation 'com.firebaseui:firebase-ui-database:1.2.0'
//noinspection GradleCompatible
implementation 'com.android.support:design:26.+'
def nav_version = "2.1.0-alpha06"
// Java
implementation "androidx.navigation:navigation-fragment:$nav_version"
implementation "androidx.navigation:navigation-ui:$nav_version"
}
apply plugin: 'com.google.gms.google-services'
apply plugin: "androidx.navigation.safeargs"
我试图搜索网络和论坛，但到目前为止，我发现没有任何帮助.
I've tried to search the web and forums but so far I didn't find anything helpful.
非常感谢您.
推荐答案
在将项目配置为使用AndroidX的同时，您正在从旧的Android支持库(android.support.v<x>)导入Fragment，因此请确保您导入并使用正确的库.
You are importing Fragment from the old Android Support library (android.support.v<x>) while you’ve configured your project to use AndroidX, so make sure you are importing and using the correct library.
请访问此链接，以找到Fragment的正确导入.
Please visit this link to find the correct import for Fragment.
用
androidx.fragment.app.Fragment替换android.support.v4.app.Fragment.
这篇关于在Android Studio中找不到符号错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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