Android: SeekBar with custom drawable

问题:

I have SeekBar with custom drawable. Progress element is not rendered from left side exactly but it is moved to right. How can I avoid this?

<SeekBar
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@android:id/summary"
    android:background="@null"

    android:progressDrawable="@drawable/seekbar"
    android:thumb="@drawable/seekbar_thumb"/>

seekbar.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item
        android:id="@android:id/background"
        android:drawable="@drawable/seekbar_background"/>
    <item android:id="@android:id/progress">
        <clip android:drawable="@drawable/seekbar_progress" />
    </item>

</layer-list>

seekbar_background.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="line">

    <stroke android:width="2dp" android:color="@color/colorNeutral" />

</shape>

seekbar_progress.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="line">

    <stroke
        android:width="4dp"
        android:color="@color/colorAccentDark" />
</shape>

EDIT:

As mentioned in comments if there will be both widths same problem disappear. But I need make it with two different widths through drawable is it possible? Maybe with different shapes not just lines?

回答1:

I can not explain why this is an issue when drawing strokes, I think it has something to do with the strokes width, but I did not yet find the source to verify.

Fixing the Overlay

To remove the issue at hand, you can just set an inset on your left side. A value of 1dp or 2dp both work and the seekbar will be drawn properly.

Note: Using this approach there should be no risk that the background could be too short and not visible with low progress values, since the thumb would overlay and hide it in any case.

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@android:id/background"
        android:drawable="@drawable/seekbar_background"
        android:left="2dp"><!-- or 1dp -->
    </item>
    <item android:id="@android:id/progress">
        <clip android:drawable="@drawable/seekbar_progress"/>
    </item>
</layer-list>

回答2:

Observation

When you create a line using shape drawable it leaves the left and right padding (from the view in which this drawable is being used.)equal to the half of its stroke width.

Workaround

You need to wrap your progress_background with an inset drawable and then set it as progress background. The inset can be like the following-

inset_seekbar_background.xml

<inset xmlns:android="http://schemas.android.com/apk/res/android"
    android:drawable="@drawable/seekbar_progress"
    android:insetLeft="2dp"
    android:insetRight="2dp" />

and your final seekbar.xml will be like-

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item
        android:id="@android:id/background"
        android:drawable="@drawable/inset_seekbar_background"/>
    <item android:id="@android:id/progress">
        <clip android:drawable="@drawable/seekbar_progress" />
    </item>

</layer-list>

Alternates

1.You can use an 9 path image for line as it is done in the default material design-

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@android:id/background"
        android:drawable="@drawable/abc_scrubber_primary_mtrl_alpha" />
    <item android:id="@android:id/secondaryProgress">
        <scale android:scaleWidth="100%">
            <selector>
                <item android:state_enabled="false">
                    <color android:color="@android:color/transparent" />
                </item>
                <item android:drawable="@drawable/abc_scrubber_primary_mtrl_alpha" />
            </selector>
        </scale>
    </item>
    <item android:id="@android:id/progress">
        <scale android:scaleWidth="100%">
            <selector>
                <item android:state_enabled="true">
                    <color android:color="@android:color/transparent" />
                </item>
                <item android:drawable="@drawable/abc_scrubber_primary_mtrl_alpha" />
            </selector>
        </scale>
    </item>
</layer-list><!-- From: file:/usr/local/google/buildbot/src/googleplex-android/mnc-supportlib-release/frameworks/support/v7/appcompat/res/drawable/abc_seekbar_track_material.xml -->

2.You can set the theme to your view with different color in android style as-

<style name="AppTheme.SeekBar">
        <item name="colorPrimary">@color/colorAccent</item>
        <item name="colorPrimaryDark">@color/colorPrimary</item>
        <item name="colorAccent">@color/colorPrimaryDark</item>
</style>

Here I have used all there options for Seekbars-

            <SeekBar 
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:theme="@style/AppTheme.SeekBar" />

            <SeekBar
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />

            <SeekBar
                android:layerType="software"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:progressDrawable="@drawable/seekbar" />

And here is the output-

回答3:

As it appear the issue in progress I think they both should be the same width

but you in progress make width = 4 android:width="4dp"

and seekbar width = 2 android:width="2dp"

just match them to be 2 or 4 dont use different values

回答4:

Try using a .9.png drawable of width 4dp (converted to px) .

Keep 1 dp at top and bottom transparent.

And add colour to the center 2 dp of your choice for the background.

This way both background and progress will be of same width but the background will look thinner than progress bar.

回答5:

If your choices of color has a limit and is predefined. You can try to add XML files with Seekbars using different themes.

Something like this:

themed_seekbar_one.xml

<?xml version="1.0" encoding="utf-8"?>
<SeekBar
    ...
    android:theme="@style/first_theme">
</SeekBar>

themed_seekbar_two.xml

<?xml version="1.0" encoding="utf-8"?>
<SeekBar
    ...
    android:theme="@style/second_theme">
</SeekBar>

You can then inflate does views programatically like this:

SeekBar seekbar = (SeekBar)getLayoutInflater().inflate(R.layout.themed_seekbar_xxx, null);

回答6:

Try like this using android:layout_marginLeft="-3dp" or -2dp

<SeekBar
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@android:id/summary"
    android:background="@null"
    android:layout_marginLeft="-2dp"
    android:progressDrawable="@drawable/seekbar"
    android:thumb="@drawable/seekbar_thumb"/>`