Question

我无法在显示的主要活动中实施进度条无法解析方法＆＃39; findViewById＆＃39;

我想知道为什么会这样显示，因为很多时候我遇到了这个问题，我是初学者，所以我要求开发人员帮助我。

这是MainActivity的代码

package com.fb.jaisonjoseph.facebookbasic;

import android.content.Context;
import android.graphics.Bitmap;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;

import android.view.KeyEvent;
 /**
  * A simple {@link Fragment} subclass.
   */
  public class Home_Fragment extends Fragment {
   public ProgressBar bar;

public WebView mwebView;

public Home_Fragment() {

    // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment

    View rootView = inflater.inflate(R.layout.fragment_home_, null);
    WebView view=(WebView) rootView.findViewById(R.id.webView);

    view.loadUrl("https://mbasic.facebook.com");
    view.getSettings().setJavaScriptEnabled(true);
    view.setWebViewClient(new MyWebViewClient());
    //bar=(ProgressBar)rootView.findViewById(R.id.progressBar);

    return rootView;
    }

 private class MyWebViewClient extends WebViewClient {
    ProgressBar bar=(ProgressBar)findViewById(R.id.progressBar);

    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        return false;
    }

    @Override
    public void onPageStarted(final WebView view, final String url, final Bitmap favicon) {
        bar.setVisibility(View.VISIBLE);

        super.onPageStarted(view, url, favicon);
    }
    @Override
    public void onPageFinished(WebView view, String url) {
        bar.setVisibility(View.GONE);

        super.onPageFinished(view, url);
    }
  }
}

此处是MainActivity的屏幕截图

活动代码

package com.fb.jaisonjoseph.facebookbasic;

 import android.app.FragmentManager;
 import android.graphics.Bitmap;
 import android.os.Bundle;
 import android.support.design.widget.FloatingActionButton;
 import android.support.design.widget.Snackbar;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.support.design.widget.NavigationView;
 import android.support.v4.view.GravityCompat;
 import android.support.v4.widget.DrawerLayout;
 import android.support.v7.app.ActionBarDrawerToggle;
 import android.support.v7.app.AppCompatActivity;
 import android.support.v7.widget.Toolbar;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.ViewGroup;
 import android.webkit.WebView;
 import android.webkit.WebViewClient;
 import android.widget.ProgressBar;

import java.security.PrivateKey;

  public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {



@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment




    View rootView = inflater.inflate(R.layout.fragment_home_, null);
    WebView view=(WebView) rootView.findViewById(R.id.webView);

    view.loadUrl("https://mbasic.facebook.com");
    view.getSettings().setJavaScriptEnabled(true);
    view.setWebViewClient(new MyWebViewClient());

   bar=(ProgressBar)rootView.findViewById(R.id.progressBar);

    return rootView;
}



private class MyWebViewClient extends WebViewClient {


    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        return false;
    }

    @Override
    public void onPageStarted(final WebView view, final String url, final Bitmap favicon) {
        bar.setVisibility(View.VISIBLE);

        super.onPageStarted(view, url, favicon);
    }
    @Override
    public void onPageFinished(WebView view, String url) {
        bar.setVisibility(View.GONE);

        super.onPageFinished(view, url);
    }
}






@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) 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 = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}


@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) 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.main, 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) {

        Home_Fragment home_fragment=new Home_Fragment();
        android.support.v4.app.FragmentManager manager=getSupportFragmentManager();
        manager.beginTransaction().replace(R.id.relative_layour_fragment, home_fragment,home_fragment.getTag()).commit();

    } else if (id == R.id.nav_profile) {
       Profile_Fragment profile_fragment=new Profile_Fragment();
        android.support.v4.app.FragmentManager manager=getSupportFragmentManager();
        manager.beginTransaction().replace(R.id.relative_layour_fragment,profile_fragment,profile_fragment.getTag()).commit();
    } else if (id == R.id.nav_messages) {

    } else if (id == R.id.nav_notifications) {

    } else if (id == R.id.nav_chat) {

    } else if (id == R.id.nav_chat) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}
}

Answer 1

你必须声明进度条全局并在OncreateView中声明如下。

import android.content.Context;
import android.graphics.Bitmap;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;

import android.view.KeyEvent;
 /**
  * A simple {@link Fragment} subclass.
   */
  public class Home_Fragment extends Fragment {
   public ProgressBar bar;

public WebView mwebView;
ProgressBar bar;

public Home_Fragment() {

    // Required empty public constructor
}



@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment




    View rootView = inflater.inflate(R.layout.fragment_home_, null);
    bar=(ProgressBar)rootView.findViewById(R.id.progressBar);
    view.loadUrl("https://mbasic.facebook.com");
    view.getSettings().setJavaScriptEnabled(true);
    view.setWebViewClient(new MyWebViewClient());
    //bar=(ProgressBar)rootView.findViewById(R.id.progressBar);

    return rootView;
    }



 private class MyWebViewClient extends WebViewClient {


    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        return false;
    }

    @Override
    public void onPageStarted(final WebView view, final String url, final Bitmap favicon) {
        bar.setVisibility(View.VISIBLE);

        super.onPageStarted(view, url, favicon);
    }
    @Override
    public void onPageFinished(WebView view, String url) {
        bar.setVisibility(View.GONE);

        super.onPageFinished(view, url);
    }
    }

}

检查我的代码希望这会有所帮助。：）

Answer 2

ProgressBar bar;//declare as global

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_home_, null);
WebView view=(WebView) rootView.findViewById(R.id.webView);

bar=(ProgressBar) rootView.findViewById(R.id.progressBar);

view.loadUrl("https://mbasic.facebook.com");
view.getSettings().setJavaScriptEnabled(true);
view.setWebViewClient(new MyWebViewClient()); 
return rootView;
}

Answer 3

看看这个解决方案

search lvalues

Answer 4

方法findViewById不属于您尝试访问它的类MyWebViewClient。

要解决此问题，您需要在片段中保留引用或ProgressBar，然后从MyWebViewClient访问它。将您的代码更改为：

package com.fb.jaisonjoseph.facebookbasic;


import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;



/**
 * A simple {@link Fragment} subclass.
 */
public class Home_Fragment extends Fragment {
    public ProgressBar bar;

    public WebView mwebView;

    public Home_Fragment() {

        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment


        View rootView = inflater.inflate(R.layout.fragment_home_, null);
        WebView view = (WebView) rootView.findViewById(R.id.webView);
        view.loadUrl("https://mbasic.facebook.com");
        view.getSettings().setJavaScriptEnabled(true);
        view.setWebViewClient(new MyWebViewClient());
        bar=(ProgressBar)rootView.findViewById(R.id.progressBar); //uncomment this

        return rootView;
    }


    private class MyWebViewClient extends WebViewClient {
// ProgressBar bar=(ProgressBar)findViewById(R.id.progressBar); Not needed

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            return false;
        }

        @Override
        public void onPageStarted(final WebView view, final String url, final Bitmap favicon) {
            bar.setVisibility(View.VISIBLE);

            super.onPageStarted(view, url, favicon);
        }

        @Override
        public void onPageFinished(WebView view, String url) {
            bar.setVisibility(View.GONE);

            super.onPageFinished(view, url);
        }
    }


}

修改

同时将您的活动代码更新为：

package com.fb.jaisonjoseph.facebookbasic; import android.app.FragmentManager; import android.graphics.Bitmap; import android.os.Bundle; import android.support.design.widget.FloatingActionButton; import android.support.design.widget.Snackbar; import android.view.LayoutInflater; import android.view.View; import android.support.design.widget.NavigationView; import android.support.v4.view.GravityCompat; import android.support.v4.widget.DrawerLayout; import android.support.v7.app.ActionBarDrawerToggle; import android.support.v7.app.AppCompatActivity; import android.support.v7.widget.Toolbar; import android.view.Menu; import android.view.MenuItem; import android.view.ViewGroup; import android.webkit.WebView; import android.webkit.WebViewClient; import android.widget.ProgressBar; import java.security.PrivateKey; public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); setSupportActionBar(toolbar); FloatingActionButton fab = (FloatingActionButton) 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 = (DrawerLayout) findViewById(R.id.drawer_layout); ActionBarDrawerToggle toggle = new ActionBarDrawerToggle( this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); drawer.setDrawerListener(toggle); toggle.syncState(); NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); navigationView.setNavigationItemSelectedListener(this); } @Override public void onBackPressed() { DrawerLayout drawer = (DrawerLayout) 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.main, 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) { Home_Fragment home_fragment=new Home_Fragment(); android.support.v4.app.FragmentManager manager=getSupportFragmentManager(); manager.beginTransaction().replace(R.id.relative_layour_fragment, home_fragment,home_fragment.getTag()).commit(); } else if (id == R.id.nav_profile) { Profile_Fragment profile_fragment=new Profile_Fragment(); android.support.v4.app.FragmentManager manager=getSupportFragmentManager(); manager.beginTransaction().replace(R.id.relative_layour_fragment,profile_fragment,profile_fragment.getTag()).commit(); } else if (id == R.id.nav_messages) { } else if (id == R.id.nav_notifications) { } else if (id == R.id.nav_chat) { } else if (id == R.id.nav_chat) { } DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); drawer.closeDrawer(GravityCompat.START); return true; } }

进度条在MainActivity中不起作用

4 个答案: