自定义SeekBar无法实例化 - java.lang.NullPointerException

Question

当我尝试在main.xml中使用自定义搜索栏时，我无法实例化错误消息，并且在运行时它会给出一个Error inflating类消息。

customseekbar.xml

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<TableRow
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView 
        android:id="@+id/leftText"
        android:textSize="10dp"
        android:gravity="left" 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <TextView 
        android:id="@+id/centerText"
        android:textSize="20dp"
        android:gravity="left"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView 
        android:id="@+id/rightText"
        android:textSize="10dp"
        android:gravity="right"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</TableRow>

<TableRow
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <SeekBar 
        android:id="@+id/seekBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"            />

</TableRow>

CustomSeekBar.java

    package kirbz.Component.CustomSeekBar;
    import android.content.Context;
    import android.util.AttributeSet;
    import android.widget.SeekBar;
    import android.widget.TextView;

public class CustomSeekBar extends SeekBar {

private SeekBar mSeekBar = (SeekBar) findViewById(R.id.seekBar);
private TextView mMinText = (TextView) findViewById(R.id.leftText);
private TextView mMaxText = (TextView) findViewById(R.id.rightText);
private TextView mValueText = (TextView) findViewById(R.id.centerText);

public CustomSeekBar(Context context, AttributeSet attrs) {
    super(context, attrs);
     mSeekBar=(SeekBar) findViewById(R.id.seekBar);
     mSeekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                mValueText.setText(String.valueOf(new Integer(progress)));        
            }

            public void onStartTrackingTouch(SeekBar arg0) {
                // TODO Auto-generated method stub
                  mValueText.setText(String.valueOf(new Integer(mSeekBar.getProgress())));      
            }

            public void onStopTrackingTouch(SeekBar arg0) {
                // TODO Auto-generated method stub
                  mValueText.setText(String.valueOf(new Integer(mSeekBar.getProgress())));      
            }
     });
    // TODO Auto-generated constructor stub
}

public void setValues(int max, int min, int value) {
    mSeekBar.setMax(max-min);
    mMaxText.setText(String.valueOf(max));
    mMinText.setText(String.valueOf(min));
    mSeekBar.setProgress(value - min);
    mValueText.setText(String.valueOf(value));

}

}

我的main.xml是

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<kirbz.Component.CustomSeekBar.CustomSeekBar
    android:id="@+id/customSeekBar1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" 
    android:layout_gravity="left" />

logcat的

05-01 17:39:51.227: E/AndroidRuntime(675): FATAL EXCEPTION: main
05-01 17:39:51.227: E/AndroidRuntime(675): java.lang.RuntimeException: Unable to start activity ComponentInfo{kirbz.Component.CustomSeekBar/kirbz.Component.CustomSeekBar.CustomSeekBarActivity}: android.view.InflateException: Binary XML file line #12: Error inflating class kirbz.Component.CustomSeekBar.CustomSeekBar
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.os.Looper.loop(Looper.java:123)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.ActivityThread.main(ActivityThread.java:3683)
05-01 17:39:51.227: E/AndroidRuntime(675):  at java.lang.reflect.Method.invokeNative(Native Method)
05-01 17:39:51.227: E/AndroidRuntime(675):  at java.lang.reflect.Method.invoke(Method.java:507)
05-01 17:39:51.227: E/AndroidRuntime(675):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-01 17:39:51.227: E/AndroidRuntime(675):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-01 17:39:51.227: E/AndroidRuntime(675):  at dalvik.system.NativeStart.main(Native Method)
05-01 17:39:51.227: E/AndroidRuntime(675): Caused by: android.view.InflateException: Binary XML file line #12: Error inflating class kirbz.Component.CustomSeekBar.CustomSeekBar
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.view.LayoutInflater.createView(LayoutInflater.java:518)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:570)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.view.LayoutInflater.rInflate(LayoutInflater.java:623)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.view.LayoutInflater.inflate(LayoutInflater.java:408)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.view.LayoutInflater.inflate(LayoutInflater.java:320)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.view.LayoutInflater.inflate(LayoutInflater.java:276)
05-01 17:39:51.227: E/AndroidRuntime(675):  at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:207)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.Activity.setContentView(Activity.java:1657)
05-01 17:39:51.227: E/AndroidRuntime(675):  at kirbz.Component.CustomSeekBar.CustomSeekBarActivity.onCreate(CustomSeekBarActivity.java:11)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
05-01 17:39:51.227: E/AndroidRuntime(675):  ... 11 more
05-01 17:39:51.227: E/AndroidRuntime(675): Caused by: java.lang.reflect.InvocationTargetException
05-01 17:39:51.227: E/AndroidRuntime(675):  at java.lang.reflect.Constructor.constructNative(Native Method)
05-01 17:39:51.227: E/AndroidRuntime(675):  at java.lang.reflect.Constructor.newInstance(Constructor.java:415)
05-01 17:39:51.227: E/AndroidRuntime(675):  at android.view.LayoutInflater.createView(LayoutInflater.java:505)
05-01 17:39:51.227: E/AndroidRuntime(675):  ... 21 more
05-01 17:39:51.227: E/AndroidRuntime(675): Caused by: java.lang.NullPointerException
05-01 17:39:51.227: E/AndroidRuntime(675):  at kirbz.Component.CustomSeekBar.CustomSeekBar.<init>(CustomSeekBar.java:18)
05-01 17:39:51.227: E/AndroidRuntime(675):  ... 24 more

你能告诉我我错过了什么吗？

感谢您的时间并提前致谢。

Answer 1

我改变了整个方法，并设法通过以下方式实现我想要的目标 -

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TableRow 
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView 
            android:id="@+id/leftText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="10dp"
            android:gravity="left" android:layout_gravity="left|center_vertical" android:layout_weight="1" android:paddingLeft="10dp"/>

        <TextView 
            android:id="@+id/centerText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20dp"
            android:gravity="center" android:layout_weight="1"/>

        <TextView 
            android:id="@+id/rightText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="10dp"
            android:gravity="right" android:layout_weight="1" android:paddingRight="10dp"/>
    </TableRow>


    <TableRow 
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <SeekBar 
            android:id="@+id/seekBar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
 />

    </TableRow>
</LinearLayout>

CustomBar.java是一个自定义类，它将布局膨胀为LAYOUT

import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.widget.LinearLayout;
import android.widget.SeekBar;
import android.widget.Toast;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.view.View;
import android.widget.TextView;

public class CustomBar extends LinearLayout {

    private SeekBar mSeekBar;
    private TextView mMinText;
    private TextView mMaxText;
    private TextView mValueText;

    public CustomBar(Context context, AttributeSet attrs) {
        super(context, attrs);
        final LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        inflater.inflate(R.layout.customseekbarlayout, this);

        initializeLayout();

        // TODO Auto-generated constructor stub

    }

    public void setValues(int max, int min, int value) {
        mSeekBar.setMax(max-min);
        mMaxText.setText(String.valueOf(max));
        mMinText.setText(String.valueOf(min));
        mSeekBar.setProgress(value - min);
        mValueText.setText(String.valueOf(value));

    }

    private void initializeLayout() {
        this.mSeekBar = (SeekBar) findViewById(R.id.seekBar);
        this.mMinText = (TextView) findViewById(R.id.leftText);
        this.mMaxText = (TextView) findViewById(R.id.rightText);
        this.mValueText = (TextView) findViewById (R.id.centerText);

        this.mSeekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

            @Override
            public void onProgressChanged(SeekBar seekBar, int progress,
                    boolean fromUser) {
                // TODO Auto-generated method stub
                mValueText.setText(String.valueOf(progress));
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                // TODO Auto-generated method stub
                //Toast.makeText(getContext(), "Test2", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                // TODO Auto-generated method stub
                //Toast.makeText(getContext(), "Test3", Toast.LENGTH_SHORT).show();
            }

        });
    }

    public int getValue(){
        return mSeekBar.getProgress();
    }


}

main.xml是

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <kirbz.Components.CustomSeekBar.CustomBar
        android:id="@+id/customBar1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </kirbz.Components.CustomSeekBar.CustomBar>

</LinearLayout>

并且MainActivity是

import android.app.Activity;
import android.os.Bundle;

    public class CustomSeekBarActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final CustomBar mSeekBar = (CustomBar) findViewById(R.id.customBar1);


        mSeekBar.setValues(8,4,6);
    }
}