爲什麼我無法看到操作欄中的向上箭頭？

Question

我需要導航到我之前的活動。我想使用動作欄（工具欄）的箭頭。我無法看到我的動作欄（工具欄）中的向上箭頭。我附上下面的活動代碼。

ImageActivity.java

public class ImageActivity extends AppCompatActivity { 

    private Toolbar toolbar; 
    int img,img1; 
    String text; 
    ImageView imgicon; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     getWindow().requestFeature(Window.FEATURE_ACTION_BAR); 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_image); 

     toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 
     getSupportActionBar().show(); 
     Drawable upArrow = ContextCompat.getDrawable(this, R.drawable.abc_ic_ab_back_mtrl_am_alpha); 
     upArrow.setColorFilter(ContextCompat.getColor(this, R.color.white), PorterDuff.Mode.SRC_ATOP); 
     getSupportActionBar().setDisplayHomeAsUpEnabled(true); 
     getSupportActionBar().setHomeAsUpIndicator(upArrow); 
     getSupportActionBar().setHomeButtonEnabled(true); 


     imgicon = (ImageView) findViewById(R.id.img); 

     Bundle bundle = getIntent().getExtras(); 

     if(bundle!=null) 
     { 
     img = bundle.getInt("img"); 
     text = bundle.getString("Phone"); 
     getSupportActionBar().setTitle("text"); 
     imgicon.setImageResource(img); 
     } 

     img1 = bundle.getInt("img1"); 
     imgicon.setImageResource(img1); 

    } 


    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     switch (item.getItemId()) { 
      case android.R.id.home: 
       //Write your logic here 
       this.finish(); 
       return true; 
      default: 
       return super.onOptionsItemSelected(item); 
     } 
    } 
} 

有沒有人遇到這種情況，不知怎麼找到了一種方法來解決呢？提前致謝。

Answer 1

請嘗試使用此

android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar); 

     try { 
      setSupportActionBar(toolbar); 

      ActionBar actionbar = getSupportActionBar(); 
      if (actionbar != null) { 
       actionbar.setHomeButtonEnabled(true); 
       actionbar.setDisplayShowHomeEnabled(true); 
       actionbar.setDisplayHomeAsUpEnabled(true); 
      } 

和XML

<android.support.v7.widget.Toolbar 
     android:id="@+id/toolbar" 
     android:layout_width="match_parent" 
     android:layout_height="?attr/actionBarSize" 
     android:background="@color/colorWhite" 
     app:popupTheme="@style/AppTheme.PopupOverlay" />