Failed to load AppCompat ActionBar with unknown error?

I had the same problem. Seems it is a Android Studio bug.

In your styles xml-file change this:

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

to this:

<style name="AppTheme" parent="Base.Theme.AppCompat.Light.DarkActionBar">

Works for me.

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unable-to-resolve-dependency error solution

just go to Settings >Gradle >Disable Offline Work 

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all colour xml

<?xml version="1.0" encoding="utf-8"?><resources>
    <color name="colorPrimary">#3F51B5</color>
    <color name="colorPrimaryDark">#303F9F</color>
    <color name="colorAccent">#FF4081</color>
    <color name="White">#FFFFFF</color>
    <color name="Ivory">#FFFFF0</color>
    <color name="LightYellow">#FFFFE0</color>
    <color name="Yellow">#FFFF00</color>
    <color name="Snow">#FFFAFA</color>
    <color name="FloralWhite">#FFFAF0</color>
    <color name="LemonChiffon">#FFFACD</color>
    <color name="Cornsilk">#FFF8DC</color>
    <color name="Seashell">#FFF5EE</color>
    <color name="LavenderBlush">#FFF0F5</color>
    <color name="PapayaWhip">#FFEFD5</color>
    <color name="BlanchedAlmond">#FFEBCD</color>
    <color name="MistyRose">#FFE4E1</color>
    <color name="Bisque">#FFE4C4</color>
    <color name="Moccasin">#FFE4B5</color>
    <color name="NavajoWhite">#FFDEAD</color>
    <color name="PeachPuff">#FFDAB9</color>
    <color name="Gold">#FFD700</color>
    <color name="Pink">#FFC0CB</color>
    <color name="LightPink">#FFB6C1</color>
    <color name="Orange">#FFA500</color>
    <color name="LightSalmon">#FFA07A</color>
    <color name="DarkOrange">#FF8C00</color>
    <color name="Coral">#FF7F50</color>
    <color name="HotPink">#FF69B4</color>
    <color name="Tomato">#FF6347</color>
    <color name="OrangeRed">#FF4500</color>
    <color name="DeepPink">#FF1493</color>
    <color name="Fuchsia">#FF00FF</color>
    <color name="Magenta">#FF00FF</color>
    <color name="Red">#FF0000</color>
    <color name="OldLace">#FDF5E6</color>
    <color name="LightGoldenrodYellow">#FAFAD2</color>
    <color name="Linen">#FAF0E6</color>
    <color name="AntiqueWhite">#FAEBD7</color>
    <color name="Salmon">#FA8072</color>
    <color name="GhostWhite">#F8F8FF</color>
    <color name="MintCream">#F5FFFA</color>
    <color name="WhiteSmoke">#F5F5F5</color>
    <color name="Beige">#F5F5DC</color>
    <color name="Wheat">#F5DEB3</color>
    <color name="SandyBrown">#F4A460</color>
    <color name="Azure">#F0FFFF</color>
    <color name="Honeydew">#F0FFF0</color>
    <color name="AliceBlue">#F0F8FF</color>
    <color name="Khaki">#F0E68C</color>
    <color name="LightCoral">#F08080</color>
    <color name="PaleGoldenrod">#EEE8AA</color>
    <color name="Violet">#EE82EE</color>
    <color name="DarkSalmon">#E9967A</color>
    <color name="Lavender">#E6E6FA</color>
    <color name="LightCyan">#E0FFFF</color>
    <color name="BurlyWood">#DEB887</color>
    <color name="Plum">#DDA0DD</color>
    <color name="Gainsboro">#DCDCDC</color>
    <color name="Crimson">#DC143C</color>
    <color name="PaleVioletRed">#DB7093</color>
    <color name="Goldenrod">#DAA520</color>
    <color name="Orchid">#DA70D6</color>
    <color name="Thistle">#D8BFD8</color>
    <color name="LightGrey">#D3D3D3</color>
    <color name="Tan">#D2B48C</color>
    <color name="Chocolate">#D2691E</color>
    <color name="Peru">#CD853F</color>
    <color name="IndianRed">#CD5C5C</color>
    <color name="MediumVioletRed">#C71585</color>
    <color name="Silver">#C0C0C0</color>
    <color name="DarkKhaki">#BDB76B</color>
    <color name="RosyBrown">#BC8F8F</color>
    <color name="MediumOrchid">#BA55D3</color>
    <color name="DarkGoldenrod">#B8860B</color>
    <color name="FireBrick">#B22222</color>
    <color name="PowderBlue">#B0E0E6</color>
    <color name="LightSteelBlue">#B0C4DE</color>
    <color name="PaleTurquoise">#AFEEEE</color>
    <color name="GreenYellow">#ADFF2F</color>
    <color name="LightBlue">#ADD8E6</color>
    <color name="DarkGray">#A9A9A9</color>
    <color name="Brown">#A52A2A</color>
    <color name="Sienna">#A0522D</color>
    <color name="YellowGreen">#9ACD32</color>
    <color name="DarkOrchid">#9932CC</color>
    <color name="PaleGreen">#98FB98</color>
    <color name="DarkViolet">#9400D3</color>
    <color name="MediumPurple">#9370DB</color>
    <color name="LightGreen">#90EE90</color>
    <color name="DarkSeaGreen">#8FBC8F</color>
    <color name="SaddleBrown">#8B4513</color>
    <color name="DarkMagenta">#8B008B</color>
    <color name="DarkRed">#8B0000</color>
    <color name="BlueViolet">#8A2BE2</color>
    <color name="LightSkyBlue">#87CEFA</color>
    <color name="SkyBlue">#87CEEB</color>
    <color name="Gray">#808080</color>
    <color name="Olive">#808000</color>
    <color name="Purple">#800080</color>
    <color name="Maroon">#800000</color>
    <color name="Aquamarine">#7FFFD4</color>
    <color name="Chartreuse">#7FFF00</color>
    <color name="LawnGreen">#7CFC00</color>
    <color name="MediumSlateBlue">#7B68EE</color>
    <color name="LightSlateGray">#778899</color>
    <color name="SlateGray">#708090</color>
    <color name="OliveDrab">#6B8E23</color>
    <color name="SlateBlue">#6A5ACD</color>
    <color name="DimGray">#696969</color>
    <color name="MediumAquamarine">#66CDAA</color>
    <color name="CornflowerBlue">#6495ED</color>
    <color name="CadetBlue">#5F9EA0</color>
    <color name="DarkOliveGreen">#556B2F</color>
    <color name="Indigo">#4B0082</color>
    <color name="MediumTurquoise">#48D1CC</color>
    <color name="DarkSlateBlue">#483D8B</color>
    <color name="SteelBlue">#4682B4</color>
    <color name="RoyalBlue">#4169E1</color>
    <color name="Turquoise">#40E0D0</color>
    <color name="MediumSeaGreen">#3CB371</color>
    <color name="LimeGreen">#32CD32</color>
    <color name="DarkSlateGray">#2F4F4F</color>
    <color name="SeaGreen">#2E8B57</color>
    <color name="ForestGreen">#228B22</color>
    <color name="LightSeaGreen">#20B2AA</color>
    <color name="DodgerBlue">#1E90FF</color>
    <color name="MidnightBlue">#191970</color>
    <color name="Aqua">#00FFFF</color>
    <color name="Cyan">#00FFFF</color>
    <color name="SpringGreen">#00FF7F</color>
    <color name="Lime">#00FF00</color>
    <color name="MediumSpringGreen">#00FA9A</color>
    <color name="DarkTurquoise">#00CED1</color>
    <color name="DeepSkyBlue">#00BFFF</color>
    <color name="DarkCyan">#008B8B</color>
    <color name="Teal">#008080</color>
    <color name="Green">#008000</color>
    <color name="DarkGreen">#006400</color>
    <color name="Blue">#0000FF</color>
    <color name="MediumBlue">#0000CD</color>
    <color name="DarkBlue">#00008B</color>
    <color name="Navy">#000080</color>
    <color name="Black">#000000</color>
    <color name="orange">#ff5500</color>
    <color name="white">#ffffff</color>
    <color name="transparent">#00000000</color>
    <color name="date_color">#999999</color>
    <color name="black">#000000</color>
    <color name="gray">#999999</color>
    <color name="blue">#0066cc</color>
    <color name="gold">#e6b121</color>
    <color name="blueback">#99FFFF</color>
    <color name="articlecolor">#3399FF</color>
    <color name="article_title">#3399FF</color>
    <color name="cachecolor">#8ad0e8</color>

    <color name="yellow">#FFFF00</color>
    <color name="fuchsia">#FF00FF</color>
    <color name="red">#FF0000</color>
    <color name="silver">#C0C0C0</color>

    <color name="olive">#808000</color>
    <color name="purple">#800080</color>
    <color name="maroon">#800000</color>
    <color name="aqua">#00FFFF</color>
    <color name="lime">#00FF00</color>
    <color name="teal">#008080</color>
    <color name="green">#008000</color>

    <color name="navy">#000080</color>


    <color name="ivory">#FFFFF0</color>
    <color name="light_yellow">#FFFFE0</color>
  
    <color name="snow">#FFFAFA</color>
    <color name="floral_white">#FFFAF0</color>
    <color name="lemon_chiffon">#FFFACD</color>
    <color name="cornsilk">#FFF8DC</color>
    <color name="seashell">#FFF5EE</color>
    <color name="lavender_blush">#FFF0F5</color>
    <color name="papaya_whip">#FFEFD5</color>
    <color name="blanched_almond">#FFEBCD</color>
    <color name="misty_rose">#FFE4E1</color>
    <color name="bisque">#FFE4C4</color>
    <color name="moccasin">#FFE4B5</color>
    <color name="navajo_white">#FFDEAD</color>
    <color name="peach_puff">#FFDAB9</color>
    <color name="cold">#FFD700</color>
    <color name="pink">#FFC0CB</color>
    <color name="light_pink">#FFB6C1</color>

    <color name="light_salmon">#FFA07A</color>
    <color name="dark_orange">#FF8C00</color>
    <color name="coral">#FF7F50</color>
    <color name="hot_pink">#FF69B4</color>
    <color name="tomato">#FF6347</color>
    <color name="orange_red">#FF4500</color>
    <color name="deep_pink">#FF1493</color>

    <color name="magenta">#FF00FF</color>

    <color name="old_lace">#FDF5E6</color>
    <color name="light_goldenrod_yellow">#FAFAD2</color>
    <color name="linen">#FAF0E6</color>
    <color name="antique_white">#FAEBD7</color>
    <color name="salmon">#FA8072</color>
    <color name="ghost_white">#F8F8FF</color>
    <color name="mint_cream">#F5FFFA</color>
    <color name="white_smoke">#F5F5F5</color>
    <color name="beige">#F5F5DC</color>
    <color name="wheat">#F5DEB3</color>
    <color name="sandy_brown">#F4A460</color>
    <color name="azure">#F0FFFF</color>
    <color name="honeydew">#F0FFF0</color>
    <color name="alice_blue">#F0F8FF</color>
    <color name="khaki">#F0E68C</color>
    <color name="light_coral">#F08080</color>
    <color name="pale_goldenrod">#EEE8AA</color>
    <color name="violet">#EE82EE</color>
    <color name="dark_salmon">#E9967A</color>
    <color name="lavender">#E6E6FA</color>
    <color name="light_cyan">#E0FFFF</color>
    <color name="burlyWood">#DEB887</color>
    <color name="plum">#DDA0DD</color>
    <color name="gainsboro">#DCDCDC</color>
    <color name="crimson">#DC143C</color>
    <color name="pale_violet_red">#DB7093</color>
    <color name="goldenrod">#DAA520</color>
    <color name="orchid">#DA70D6</color>
    <color name="thistle">#D8BFD8</color>
    <color name="light_grey">#D3D3D3</color>
    <color name="tan">#D2B48C</color>
    <color name="chocolate">#D2691E</color>
    <color name="peru">#CD853F</color>
    <color name="indian_red">#CD5C5C</color>
    <color name="medium_violet_red">#C71585</color>

    <color name="dark_khaki">#BDB76B</color>
    <color name="rosy_brown">#BC8F8F</color>
    <color name="medium_orchid">#BA55D3</color>
    <color name="dark_goldenrod">#B8860B</color>
    <color name="fire_brick">#B22222</color>
    <color name="powder_blue">#B0E0E6</color>
    <color name="light_steel_blue">#B0C4DE</color>
    <color name="pale_turquoise">#AFEEEE</color>
    <color name="greenYellow">#ADFF2F</color>
    <color name="light_blue">#ADD8E6</color>
    <color name="dark_gray">#A9A9A9</color>
    <color name="brown">#A52A2A</color>
    <color name="sienna">#A0522D</color>
    <color name="yellow_green">#9ACD32</color>
    <color name="dark_orchid">#9932CC</color>
    <color name="pale_green">#98FB98</color>
    <color name="dark_violet">#9400D3</color>
    <color name="mediumPurple">#9370DB</color>
    <color name="_light_green">#90EE90</color>
    <color name="dark_sea_green">#8FBC8F</color>
    <color name="saddle_brown">#8B4513</color>
    <color name="dark_magenta">#8B008B</color>
    <color name="dark_red">#8B0000</color>
    <color name="blue_violet">#8A2BE2</color>
    <color name="light_sky_blue">#87CEFA</color>
    <color name="sky_blue">#87CEEB</color>

    <color name="aquamarine">#7FFFD4</color>
    <color name="chartreuse">#7FFF00</color>
    <color name="lawn_green">#7CFC00</color>
    <color name="medium_slate_blue">#7B68EE</color>
    <color name="light_slate_gray">#778899</color>
    <color name="slate_gray">#708090</color>
    <color name="olive_drab">#6B8E23</color>
    <color name="slate_blue">#6A5ACD</color>
    <color name="dim_gray">#696969</color>
    <color name="medium_aquamarine">#66CDAA</color>
    <color name="cornflower_blue">#6495ED</color>
    <color name="cadet_blue">#5F9EA0</color>
    <color name="dark_olive_green">#556B2F</color>
    <color name="indigo">#4B0082</color>
    <color name="medium_turquoise">#48D1CC</color>
    <color name="dark_slate_blue">#483D8B</color>
    <color name="steel_blue">#4682B4</color>
    <color name="royal_blue">#4169E1</color>
    <color name="turquoise">#40E0D0</color>
    <color name="medium_sea_green">#3CB371</color>
    <color name="lime_green">#32CD32</color>
    <color name="dark_slate_gray">#2F4F4F</color>
    <color name="sea_green">#2E8B57</color>
    <color name="forest_green">#228B22</color>
    <color name="light_sea_green">#20B2AA</color>
    <color name="dodger_blue">#1E90FF</color>
    <color name="midnight_blue">#191970</color>

    <color name="cyan">#00FFFF</color>
    <color name="spring_green">#00FF7F</color>

    <color name="medium_spring_green">#00FA9A</color>
    <color name="dark_turquoise">#00CED1</color>
    <color name="deep_sky_blue">#00BFFF</color>
    <color name="dark_cyan">#008B8B</color>

    <color name="dark_green">#006400</color>

    <color name="medium_blue">#0000CD</color>
    <color name="dark_blue">#00008B</color>

</resources>

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firebase test

1. a

package com.example.raj.firebasehindi;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.firebase.client.Firebase;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class MainActivity extends AppCompatActivity {
Button bt;
Firebase url;
    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Write a message to the database       // FirebaseDatabase database = FirebaseDatabase.getInstance();       // DatabaseReference myRef = database.getReference("message");
      //  myRef.setValue("Hello, World!");        Firebase.setAndroidContext(this);
        bt=(Button)findViewById(R.id.button);
        url=new Firebase("https://fir-test-e769d.firebaseio.com/");
        bt.setOnClickListener(new View.OnClickListener() {
            @Override            public void onClick(View view) {
Firebase firebase=url.child("Name");
firebase.setValue("htd");
            }
        });
    }
}

2. 1
3. 1
4. 1
5. 1

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Render problem Failed to load AppCompat ActionBar with unknown error.

REPLACE 3 WITH 1 

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LAYOUT IN ANDROID

https://www.androidhive.info/2011/07/android-layouts-linear-layout-relative-layout-and-table-layout/

1. Linear Layout
2. Relative Layout
3. Table Layout
4. Grid View
5. Tab Layout
6. List View

1. Linear Layout

In a linear layout, like the name suggests, all the elements are displayed in a linear fashion(below is an example of the linear layouts), either Horizontally or Vertically and this behavior is set in android:orientation which is an attribute of the node LinearLayout.

Example of Vertical layout snippet

<LinearLayout android:orientation="vertical"> .... </LinearLayout>
Example of Horizontal layout snippet

<LinearLayout android:orientation="horizontal"> .... </LinearLayout>
Android Layout

2. Relative Layout

In a relative layout every element arranges itself relative to other elements or a parent element.
As an example, lets consider the layout defined below. The “Cancel” button is placed relatively, to the right of the “Login” button parallely. Here is the code snippet that achieves the mentioned alignment (Right of Login button parallely)

Example code snippet

<Button android:id="@+id/btnLogin" ..></Button>

<Button android:layout_toRightOf="@id/btnLogin"
            android:layout_alignTop="@id/btnLogin" ..></Button>

3. Table Layout

Table layouts in Android works in the same way HTML table layouts work. You can divide your layouts into rows and columns. Its very easy to understand. The image below should give you an idea.

Table layout

<!-- Row 2 with 3 columns -->

    <TableRow 

        android:id="@+id/tableRow1" 

        android:layout_height="wrap_content" 

        android:layout_width="match_parent">  

        <TextView 

            android:id="@+id/TextView04" android:text="Row 2 column 1"

            android:layout_weight="1" android:background="#dcdcdc"

            android:textColor="#000000"

            android:padding="20dip" android:gravity="center"/>  

        <TextView 

            android:id="@+id/TextView04" android:text="Row 2 column 2"

            android:layout_weight="1" android:background="#d3d3d3"

            android:textColor="#000000"

            android:padding="20dip" android:gravity="center"/>

        <TextView 

            android:id="@+id/TextView04" android:text="Row 2 column 3"

            android:layout_weight="1" android:background="#cac9c9"

            android:textColor="#000000"

            android:padding="20dip" android:gravity="center"/>

    </TableRow> 

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