OnSeekBarChangeListener始终计算为NULL的Andr​​oid [英] OnSeekBarChangeListener always evaluates to null in Android

问题描述

我有，我有4个seekbars和4 textviews使陪伴每一个搜索栏的Andr​​oid程序。现在，我试图让每个TextView中的内容等于seekbars的整数进展。这是我的code，因为它代表，我已经尝试了许多方法来正确地贯彻OnSeekBarChangeListener，但仍LogCat中表明，它为空时SB1-SB4其设置为OnSeekBarChangeListener OnSeekBarProgress。请帮我找出我的问题：（

 公共类TippopotamusActivity延伸活动{
    搜索栏SB1;
    搜索栏SB2;
    搜索栏SB3;
    搜索栏SB4;
    TextView的TV1;
    TextView中TV2;
    TextView的TV3;
    TextView的TV4;/ **当第一次创建活动调用。 * /
@覆盖
公共无效的onCreate（捆绑savedInstanceState）{
    TV1 =（的TextView）findViewById（R.id.textView1）;
    TV2 =（的TextView）findViewById（R.id.textView2）;
    TV3 =（的TextView）findViewById（R.id.textView3）;
    TV4 =（的TextView）findViewById（R.id.textView4）;    SB1 =（搜索栏）findViewById（R.id.seekBar1）;
    SB2 =（搜索栏）findViewById（R.id.seekBar2）;
    SB3 =（搜索栏）findViewById（R.id.seekBar3）;
    SB4 =（搜索栏）findViewById（R.id.seekBar4）;    sb1.setOnSeekBarChangeListener（OnSeekBarProgress）;
    sb2.setOnSeekBarChangeListener（OnSeekBarProgress）;
    sb3.setOnSeekBarChangeListener（OnSeekBarProgress）;
    sb4.setOnSeekBarChangeListener（OnSeekBarProgress）;    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.main）;
}OnSeekBarChangeListener OnSeekBarProgress =
        新OnSeekBarChangeListener（）{        公共无效onProgressChanged（搜索栏S，INT进步，布尔型触摸）{
            如果（s.getId（）== R.id.seekBar1）
            {
                tv1.setText（进度）;
            }
            否则如果（s.getId（）== R.id.seekBar2）
            {
                tv2.setText（进度）;
            }
            否则如果（s.getId（）== R.id.seekBar3）
            {
                tv3.setText（进度）;
            }
            其他
            {
                tv4.setText（进度）;
            }
        }        公共无效onStartTrackingTouch（搜索栏S）{        }        公共无效onStopTrackingTouch（搜索栏S）{        }
        };
 

解决方案

移动你的的setContentView（R.layout.main）; 初始化的变量之前。你的的onCreate 方法应该是这样的。

  / **第一次创建活动时调用。 * /
@覆盖
公共无效的onCreate（捆绑savedInstanceState）{    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.main）;    TV1 =（的TextView）findViewById（R.id.textView1）;
    TV2 =（的TextView）findViewById（R.id.textView2）;
    TV3 =（的TextView）findViewById（R.id.textView3）;
    TV4 =（的TextView）findViewById（R.id.textView4）;    SB1 =（搜索栏）findViewById（R.id.seekBar1）;
    SB2 =（搜索栏）findViewById（R.id.seekBar2）;
    SB3 =（搜索栏）findViewById（R.id.seekBar3）;
    SB4 =（搜索栏）findViewById（R.id.seekBar4）;    sb1.setOnSeekBarChangeListener（OnSeekBarProgress）;
    sb2.setOnSeekBarChangeListener（OnSeekBarProgress）;
    sb3.setOnSeekBarChangeListener（OnSeekBarProgress）;
    sb4.setOnSeekBarChangeListener（OnSeekBarProgress）;
}
 

I have an android program that I am making with 4 seekbars, and 4 textviews to accompany each seekbar. Right now, I am trying to make each textview's contents equal to the integer progress of the seekbars. This is my code as it stands, and I have tried many ways to properly implement the OnSeekBarChangeListener, but LogCat still shows that it is null when sb1-sb4 sets their OnSeekBarChangeListener to OnSeekBarProgress. Please help me identify my problem :(

public class TippopotamusActivity extends Activity {
    SeekBar sb1;
    SeekBar sb2;
    SeekBar sb3;
    SeekBar sb4;
    TextView tv1;
    TextView tv2;
    TextView tv3;
    TextView tv4;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    tv1 = (TextView) findViewById(R.id.textView1);
    tv2 = (TextView) findViewById(R.id.textView2);
    tv3 = (TextView) findViewById(R.id.textView3);
    tv4 = (TextView) findViewById(R.id.textView4);

    sb1 = (SeekBar) findViewById(R.id.seekBar1);
    sb2 = (SeekBar) findViewById(R.id.seekBar2);
    sb3 = (SeekBar) findViewById(R.id.seekBar3);
    sb4 = (SeekBar) findViewById(R.id.seekBar4);

    sb1.setOnSeekBarChangeListener(OnSeekBarProgress);
    sb2.setOnSeekBarChangeListener(OnSeekBarProgress);
    sb3.setOnSeekBarChangeListener(OnSeekBarProgress);
    sb4.setOnSeekBarChangeListener(OnSeekBarProgress);

    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
}

OnSeekBarChangeListener OnSeekBarProgress =
        new OnSeekBarChangeListener() {

        public void onProgressChanged(SeekBar s, int progress, boolean touch){
            if(s.getId() == R.id.seekBar1)
            {
                tv1.setText(progress);
            }
            else if(s.getId() == R.id.seekBar2)
            {
                tv2.setText(progress);
            }
            else if(s.getId() == R.id.seekBar3)
            {
                tv3.setText(progress);
            }
            else
            {
                tv4.setText(progress);
            }
        }

        public void onStartTrackingTouch(SeekBar s){

        }

        public void onStopTrackingTouch(SeekBar s){

        }
        };

解决方案

Move your setContentView(R.layout.main); before initializing your variables. Your onCreate method should look like this

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    tv1 = (TextView) findViewById(R.id.textView1);
    tv2 = (TextView) findViewById(R.id.textView2);
    tv3 = (TextView) findViewById(R.id.textView3);
    tv4 = (TextView) findViewById(R.id.textView4);

    sb1 = (SeekBar) findViewById(R.id.seekBar1);
    sb2 = (SeekBar) findViewById(R.id.seekBar2);
    sb3 = (SeekBar) findViewById(R.id.seekBar3);
    sb4 = (SeekBar) findViewById(R.id.seekBar4);

    sb1.setOnSeekBarChangeListener(OnSeekBarProgress);
    sb2.setOnSeekBarChangeListener(OnSeekBarProgress);
    sb3.setOnSeekBarChangeListener(OnSeekBarProgress);
    sb4.setOnSeekBarChangeListener(OnSeekBarProgress);
}

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