我做了一个简化的实验来确定我在哪里遇到这个问题。这是一个很长的问题，前面有很多代码。现在我保留了一个小而简单的代码:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_spinner_test);

    Spinner spin1 = (Spinner) findViewById(R.id.spin1);
    spin1.setAdapter(new ProfileSpinnerAdapter(this, R.array.feet));
    spin1.setSelection(0);  //does not crash
    spin1.setSelection(getResources().getStringArray(R.array.feet).length - 1);  //it crashes
   //it crashes for any value greater than 0 and less than array length.

这是错误:

java.lang.NullPointerException: Attempt to read from field 'int android.view.ViewGroup$LayoutParams.width' on a null object reference
    at android.widget.TextView.checkForRelayout(TextView.java:6830)
    at android.widget.TextView.onRtlPropertiesChanged(TextView.java:8948)
    at android.view.View.resolveRtlPropertiesIfNeeded(View.java:13118)
    at android.view.View.measure(View.java:17557)
    at android.widget.Spinner.setUpChild(Spinner.java:657)
    at android.widget.Spinner.makeView(Spinner.java:610)
    at android.widget.Spinner.getBaseline(Spinner.java:456)
    at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1294)
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
    at android.view.View.measure(View.java:17562)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
    at android.view.View.measure(View.java:17562)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
    at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
    at android.view.View.measure(View.java:17562)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2871) 
    at android.view.View.measure(View.java:17562)
    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5891)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
    at android.view.Choreographer.doCallbacks(Choreographer.java:580)
    at android.view.Choreographer.doFrame(Choreographer.java:550)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5294)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)

出现这个错误是因为我设置了layout_width=0dp。但同时 layout_weight = 1。 注意:微调器在 setSelection(0) 时正确充气。所以问题不在于直接通货膨胀。

这是 xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
tools:context="in.jiyofit.the_app.SpinnerTestActivity">

<Spinner
    android:id="@+id/spin1"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="1" />

如果 layout_width = Any non zero dp or match_parent or wrap_content while there is no layout_weight，整个代码完美。

但是使用上面相同的布局，下面的代码可以正常工作，没有崩溃:

    Spinner spin1 = (Spinner) findViewById(R.id.spin1);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
            R.array.feet, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spin1.setAdapter(adapter);
    spin1.setSelection(getResources().getStringArray(R.array.feet).length - 1);

因此我可以得出结论，我制作的 ProfileSpinnerAdapter 类存在一些问题，它与 layout_weight = 1 和 width = 0dp 冲突

这是适配器:

public class ProfileSpinnerAdapter extends BaseAdapter {
String[] array;
Context ctx;

public ProfileSpinnerAdapter(Context context, int arrayID) {
    this.ctx = context;
    this.array = ctx.getResources().getStringArray(arrayID);
}

@Override
public int getCount() {
    return array.length;
}

@Override
public Object getItem(int position) {
    return array[position];
}

@Override
public long getItemId(int position) {
    return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    TextView textView = new TextView(ctx);
    textView.setText(array[position]);
    textView.setTextSize(16);
    if(array[position].length() > 6){
        Typeface hindiFont = Typeface.createFromAsset(ctx.getAssets(),"fonts/mfdev010.ttf");
        textView.setTextSize(22);
        textView.setTypeface(hindiFont);
    }
    if(position == 0){
        textView.setTextColor(ContextCompat.getColor(ctx, R.color.primaryText));
    }
    return textView;
}

@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
    TextView textView = new TextView(ctx);
    textView.setText(array[position]);
    textView.setTextSize(16);
    textView.setPadding(0, 5, 0, 0);
    if(array[position].length() > 6){
        Typeface hindiFont = Typeface.createFromAsset(ctx.getAssets(),"fonts/mfdev010.ttf");
        textView.setTextSize(22);
        textView.setTypeface(hindiFont);
        textView.setPadding(10,5,10,5);
    }
    textView.setBackgroundColor(ContextCompat.getColor(ctx, R.color.white));
    textView.setTextColor(ContextCompat.getColor(ctx, R.color.primaryText));
    textView.setGravity(Gravity.CENTER);
    /*
    the adapter fills the number of elements based in the getCount
    so either getCount returns value conditionally for an array of different size in getDropDownView
    or the requisite value at position is hidden
    */
    if(position == 0){
        textView.setVisibility(View.GONE);
        textView.setHeight(0);
    }
    return textView;
}
}

错误的原因在适配器中。 如果 spinner width = 100dp 则不会报错，只有当 layout_weight 属性放在 spinner 上时才会报错

最佳答案

spin1.setSelection(0);  //does not crash
spin1.setSelection(getResources().getStringArray(R.array.feet).length - 1); 

改为

spin1.setSelection(0, true); 
spin1.setSelection(getResources().getStringArray(R.array.feet).length - 1, true); 

我也有这个问题并解决了

关于android - 当 layout_weight 分配给微调器时微调器上的 SetSelection 崩溃，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36447078/