In my fragment class, I create an object of my Activity class:
MainActivity mainActivity;
and in my fragment's OnCreateView(), I initialize it:
mainActivity = new MainActivity();
However, when I debug my app, mainActivity is always null. Why is this?
My Activity class:
package com.example.brettrosen.atls;
import android.annotation.TargetApi;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
#TargetApi(Build.VERSION_CODES.HONEYCOMB)
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
public ActionBar actionBar;
// Tab titles
private String[] tabs = {"Pre-arrival Plan", "Primary Survey", "Secondary Survey"};
#TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initialization
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name).setTabListener(this));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
updateTabTitles(0, 12);
updateTabTitles(1, 2);
updateTabTitles(2, 14);
}
public void updateTabTitles(int pageNum, int remaining) {
String text = tabs[pageNum] + " (" + remaining + ")";
System.out.println(actionBar);
actionBar.getTabAt(pageNum).setText(text);
}
#Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
};
I see your problem is that you want to access MainActivity from within a fragment that it hosts.
To do that, you could just call this:
getActivity();
And it will return your MainAcitvity (or any other Activity that is currently hosting your Fragment).
To access a method from it, you'd have to cast the return of that method.
MainActivity yourMain = (MainActivity) getActivity();
yourMain.method1();
Remember to do this inside of your fragment.
Related
I have looked at every tutorial on the Internet about swipeable tab views with Android. Every time I use a different code, it crashes! The logcat gives this error:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual
method 'void android.app.ActionBar.setNavigationMode(int)' on a null
object reference
I have no idea why this does not work. Here is my MainActivity code:
public class MainActivity extends FragmentActivity implements
ActionBar.TabListener {
private ViewPager viewPager;
private ActionBar actionBar;
private TabsPagerAdapter tabPagerAdapter;
private String[] tabs = {"Missed Calls", "Dialled", "Received"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager) findViewById(R.id.pager);
tabPagerAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(tabPagerAdapter);
actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
/**
* on swipe select the respective tab
* */
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
I think you are getting null value of actionBar here:
actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
change to
actionBar = getSupportActionBar();
using the import:
import android.support.v7.app.ActionBarActivity;
and remember, you have to extend from ActionBarActivity
public class MainActivity extends ActionBarActivity {
More info:
If you are using the support library
import android.support.v7.app.ActionBarActivity;
public class MainActivity extends ActionBarActivity {
use
getSupportActionBar()
instead of getActionBar()
I am new to Android Studio..I am getting following error in Android Studio.."Can't resolve method getActionBar()' in the statement actionBar = getActionBar();..Project was running fine in Eclipse..plzz Help me with this error
package info.androidhive.tabsswipe;
import com.facebooklogin.R;
import info.androidhive.tabsswipe.adapter.TabsPagerAdapter;
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.support.v4.app.Fragment;
public class MainActivity extends FragmentActivity implements
ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Top Rated", "Games", "Movies" };
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main3);
// Initilization
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// on tab selected
// show respected fragment view
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
}
if your target API is below hony must do change these lines:
Create your activity by extending ActionBarActivity.
ActionBar actionBar = getSupportActionBar();
Use (or extend) one of the Theme.AppCompat themes for your activity
I think you confuse API versions, for example you must call getSupportFragmentManager() in low API and getFragmentManager() on above API 11 and you do not need extend FragmentActivity in API 11 and above because it actually have all functions
So I am "playing" around with some code i got from a tutorial on Tab layout with swipeable views..
My Problem is that I cannot figure out how to change the default tab it opens, when the app is launched.. Right now it starts in the 1st tab(Top Rated) but I want to have it start the second tab called Games?
I've browsed around and looked for solutions but doesn't seem to find one that fits my code..
Here is my main acitivity:
package info.androidhive.tabsswipe;
import info.androidhive.tabsswipe.adapter.TabsPagerAdapter;
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
public class MainActivity extends FragmentActivity implements
ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Top Rated", "Games", "Movies" };
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initilization
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// on tab selected
// show respected fragment view
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
}
In your addTab call, add the one you want set first followed by the rest.
So change
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
to
actionBar.addTab(actionBar.newTab().setText(tabs[1])
.setTabListener(this), 1, true);
actionBar.addTab(actionBar.newTab().setText(tabs[0])
.setTabListener(this), 0, false);
actionBar.addTab(actionBar.newTab().setText(tabs[2])
.setTabListener(this), 2, false);
See Android ActionBar tabs set initially selected tab
I am trying to build a simple three (3) tabs app. I am supposed to be implementing three public methods of ActionBar.TabListener.
I believe that is exactly what I am doing in the below code. The compiler however believes that I do not. All three come with the error: "method does not override or implement a method from supertype"
I checked methods' signatures, do not even know where to look, now.
Please advise.
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.support.v4.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v4.app.FragmentActivity;
public class InSync extends FragmentActivity implements ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Backup", "Restore", "Settings"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_in_sync);
// Initilization
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// on tab selected
// show respected fragment view
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
}
Thank you.
I believe, you messed up with support libraries. Try
import android.app.FragmentTransaction;
instead of
import android.support.v4.app.FragmentTransaction;
Upd.
Or better use only support libraries:
import android.support.v4.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v4.app.FragmentActivity;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBar.Tab;
The methods you try to implement are
void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft)
void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft)
and
void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft)
I guess the Tab class you are using is not the "right" Tab class.
EDIT:
On this link you can see that there is a certain android.app.FragmentTransaction. However, you have imported android.support.v4.app.FragmentTransaction. Isn't it possible that this is the problem, as the links to FragmentTransaction from here point to the page of android.app.FragmentTransaction. I believe you should have this code:
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v4.app.FragmentActivity;
public class InSync extends FragmentActivity implements ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Backup", "Restore", "Settings"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_in_sync);
// Initilization
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
public void onTabSelected(ActionBar.Tab tab, android.app.FragmentTransaction ft) {
// on tab selected
// show respected fragment view
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(ActionBar.Tab tab, android.app.FragmentTransaction ft) {
}
#Override
public void onTabReselected(ActionBar.Tab tab, android.app.FragmentTransaction ft) {
}
}
and if it works you can test even without namespaces.
I am trying to developing Tab Navigation app in Android. I have three tab. Every tab is swipable.
MainClass extends SherlockFragmentActivity from where tab are created. Every class is extends SherlockFragment.
If i swipe tab then i need to change ActionBar custom view and title . But i can not access getSupportActionBar()
method from SherlockFragment class. How can i do that.
Can anyone please help me.
Thanks in Advance
MainActivity.java
import info.androidhive.tabsswipe.adapter.TabsPagerAdapter;
import info.androidhive.tabsswipe.R;
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.view.Menu;
public class MainActivity extends FragmentActivity implements
ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Top Rated", "Games", "Movies" };
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initilization
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// on tab selected
// show respected fragment view
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
}
Use the above code and try it with the following sample link.. This link has the source..
Source link click here: Android Tab Layout with Swipeable Views.